Coating Compositions for Cans and Methods of Coating

ABSTRACT

A coating composition for a food or beverage can that includes an emulsion polymerized latex polymer formed by combining an ethylenically unsaturated monomer component with an aqueous dispersion of a water-dispersible polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. applicationSer. No. 11/253,161, filed Oct. 18, 2005, now U.S. Pat. No. ______,which claims priority to U.S. Provisional Patent Application Ser. No.60/620,639, filed Oct. 20, 2004, each of which is incorporated herein byreference in its entirety.

BACKGROUND

A wide variety of coatings have been used to coat the surfaces ofpackaging articles (e.g., food and beverage cans). For example, metalcans are sometimes coated using “coil coating” or “sheet coating”operations, i.e., a planar coil or sheet of a suitable substrate (e.g.,steel or aluminum metal) is coated with a suitable composition andhardened (e.g., cured). The coated substrate then is formed into the canend or body. Alternatively, liquid coating compositions may be applied(e.g., by spraying, dipping, rolling, etc.) to the formed article andthen hardened (e.g., cured).

Packaging coatings should preferably be capable of high-speedapplication to the substrate and provide the necessary properties whenhardened to perform in this demanding end use. For example, the coatingshould be safe for food contact, have excellent adhesion to thesubstrate, and resist degradation over long periods of time, even whenexposed to harsh environments.

Many current packaging coatings contain mobile or bound bisphenol A(“BPA”) or aromatic glycidyl ether compounds or PVC compounds. Althoughthe balance of scientific evidence available to date indicates that thesmall trace amounts of these compounds that might be released fromexisting coatings does not pose any health risks to humans, thesecompounds are nevertheless perceived by some people as being potentiallyharmful to human health.

From the foregoing, it will be appreciated that what is needed in theart is a packaging container (e.g., a food or beverage can) that iscoated with a composition that does not contain extractible quantitiesof such compounds.

SUMMARY

This invention provides a coating composition for a food or beverage canthat includes an emulsion polymerized latex polymer. This polymer ispreferably formed by combining an ethylenically unsaturated monomercomponent with an aqueous dispersion of a salt of an acid- oranhydride-functional polymer (i.e., an acid group- or anhydridegroup-containing polymer) and an amine, preferably, a tertiary amine,and then polymerizing the monomer component. In other embodiments, thelatex polymer is alternatively formed by combining the ethylenicallyunsaturated monomer component with an aqueous dispersion of a polymersalt or other water-dispersible polymer, which may or may not includeneutralized acid or anhydride groups. For example, the water-dispersiblepolymer may include any suitable water-dispersing groups, such asanionic salt groups, cationic salt groups, non-ionic water-dispersinggroups, or combinations thereof, to facilitate formation of a stableaqueous dispersion.

The ethylenically unsaturated monomer component is preferably a mixtureof monomers. In some embodiments, at least one of the monomers in themixture is preferably an alpha, beta-unsaturated monomer, and at leastone monomer is preferably an oxirane functional monomer. Morepreferably, at least one of the monomers in the mixture is an oxiranegroup-containing alpha, beta-ethylenically unsaturated monomer.

In one embodiment, a method of preparing a food or beverage can isprovided. The method includes: forming a composition that includes anemulsion polymerized latex polymer, including: forming a salt of anacid- or anhydride-functional polymer and an amine in a carriercomprising water (and an optional organic solvent) to form an aqueousdispersion; combining an ethylenically unsaturated monomer componentwith the aqueous dispersion; and polymerizing the ethylenicallyunsaturated monomer component in the presence of the aqueous dispersionto form an emulsion polymerized latex polymer; and applying thecomposition including the emulsion polymerized latex polymer to a metalsubstrate prior to or after forming the metal substrate into a food orbeverage can or portion thereof. In other embodiments, the above methodutilizes an aqueous dispersion that includes a polymer salt having (i)salt groups formed from salt-forming groups other than acid or anhydridegroups and/or (ii) neutralizing agents other than amines.

In another embodiment, the method includes: forming a compositionincluding an emulsion polymerized latex polymer, including: forming asalt of an acid- or anhydride-functional polymer and a tertiary amine ina carrier comprising water (and an optional organic solvent) to form anaqueous dispersion; combining an ethylenically unsaturated monomercomponent comprising 0.1 percent by weight (wt-%) to 30 wt-% of anoxirane-functional alpha, beta-ethylenically unsaturated monomer withthe aqueous dispersion, based on the weight of the monomer component;and polymerizing the ethylenically unsaturated monomer component in thepresence of the aqueous dispersion to form an emulsion polymerized latexpolymer; and applying the composition comprising the emulsionpolymerized latex polymer to a metal substrate prior to or after formingthe metal substrate into a food or beverage can or portion thereof.

In certain embodiments, the composition can include an organic solventin the aqueous dispersion. In certain embodiments, the method caninclude removing at least a portion of the organic solvent, if present,from the aqueous dispersion.

In certain embodiments, applying the composition to a metal substrateincludes applying the composition to the metal substrate in the form ofa planar coil or sheet, hardening the emulsion polymerized latexpolymer, and forming the substrate into a food or beverage can orportions thereof. In certain embodiments, applying the composition to ametal substrate comprises applying the composition to the metalsubstrate after the metal substrate is formed into a can or portionthereof.

In certain embodiments, forming the substrate into a can or portionthereof includes forming the substrate into a can end or a can body. Incertain embodiments, the can is a two-piece drawn food can, three-piecefood can, food can end, drawn and ironed food or beverage can, beveragecan end, and the like. The metal substrate can be steel or aluminum.

In certain embodiments, combining an ethylenically unsaturated monomercomponent with the aqueous dispersion includes adding the ethylenicallyunsaturated monomer component to the aqueous dispersion. Theethylenically unsaturated monomer component may be added incrementallyto the aqueous dispersion, or in a batch addition.

In certain embodiments, the ethylenically unsaturated monomer componentincludes a mixture of monomers. Preferably, the mixture of monomersincludes at least one oxirane functional group-containing monomer, andmore preferably, at least one oxirane functional group-containing alpha,beta-ethylenically unsaturated monomer. In certain embodiments, theoxirane functional group-containing monomer is present in theethylenically unsaturated monomer component in an amount of at least 0.1wt-%, based on the weight of the monomer mixture. In certainembodiments, the oxirane functional group-containing monomer is presentin the ethylenically unsaturated monomer component in an amount of nogreater than 30 wt-%, based on the weight of the monomer mixture. Insome embodiments, the unsaturated monomer component does not include anymonomers having oxirane groups.

In certain embodiments, the methods of the present invention furtherinclude combining the emulsion polymerized latex polymer with one ormore crosslinkers, fillers, catalysts, dyes, pigments, toners,extenders, lubricants, anticorrosion agents, flow control agents,thixotropic agents, dispersing agents, antioxidants, adhesion promoters,light stabilizers, organic solvents, surfactants or combinations thereofin the coating composition.

In certain embodiments, the acid-functional polymer has a number averagemolecular weight of 1500 to 50,000.

In certain embodiments, the composition is substantially free of mobileBPA and aromatic glycidyl ether compounds. Preferably, the compositionis substantially free of bound BPA and aromatic glycidyl ethercompounds.

In certain embodiments, the acid- or anhydride-functional polymerincludes an acid- or anhydride-functional acrylic polymer, acid- oranhydride-functional alkyd resin, acid- or anhydride-functionalpolyester resin, acid- or anhydride-functional polyurethane, orcombinations thereof. Preferably, the acid- or anhydride-functionalpolymer includes an acid-functional acrylic polymer. In otherembodiments, the polymer (e.g., acrylic, alkyd, polyester, and/orpolyurethane) used to form the aqueous dispersion may include anysuitable combination of salt groups, salt-forming groups, or non-ionicwater-dispersing groups. In some embodiments, the polymer of the aqueousdispersion may include anionic salt groups, cationic salt groups,salt-forming groups that yield an anionic or cationic salt group (e.g.,when neutralized with a suitable acid or base), non-ionicwater-dispersing groups, or a combination thereof. In certainembodiments, the amine is a tertiary amine. Preferably, the tertiaryamine is selected from the group consisting of trimethyl amine,dimethylethanol amine (also known as dimethylamino ethanol),methyldiethanol amine, triethanol amine, ethyl methyl ethanol amine,dimethyl ethyl amine, dimethyl propyl amine, dimethyl 3-hydroxy-1-propylamine, dimethylbenzyl amine, dimethyl 2-hydroxy-1-propyl amine, diethylmethyl amine, dimethyl 1-hydroxy-2-propyl amine, triethyl amine,tributyl amine, N-methyl morpholine, and mixtures thereof. Preferably,the acid- or anhydride-functional polymer is at least 25% neutralizedwith the amine in water.

In certain embodiments, the ethylenically unsaturated monomer componentis polymerized in the presence of the aqueous dispersion with awater-soluble free radical initiator at a temperature of 0° C. to 100°C. In certain embodiments, the free radical initiator includes aperoxide initiator. In certain embodiments, the free radical initiatorincludes hydrogen peroxide and benzoin. Alternatively, in certainembodiments the free radical initiator includes a redox initiatorsystem.

The present invention also provides food cans and beverage cans preparedby a method described herein.

In one embodiment, the present invention provides a food or beverage canthat includes: a body portion or an end portion including a metalsubstrate; and a coating composition disposed thereon, wherein thecoating composition includes an emulsion polymerized latex polymer,wherein the emulsion polymerized latex polymer is prepared from a saltof an acid- or anhydride-functional polymer and an amine, anethylenically unsaturated monomer component, and water. In otherembodiments, the emulsion polymerized latex polymer of the food orbeverage can coating includes a different polymer salt in addition to,or in place of, the salt of an acid- or anhydride-functional polymer.

In yet another embodiment, the present invention provides a compositionfor use in coating a food or beverage can, wherein the compositionincludes an emulsion polymerized latex polymer, wherein the emulsionpolymerized latex polymer is prepared from a salt of an acid- oranhydride-functional polymer and an amine, an ethylenically unsaturatedmonomer component, and water. In other embodiments, the emulsionpolymerized latex polymer of the coating composition includes adifferent polymer salt in addition to, or in place of, the salt of anacid- or anhydride-functional polymer.

Definitions

The term “substantially free” of a particular mobile compound means thatthe compositions of the present invention contain less than 1000 partsper million (ppm) of the recited mobile compound. The term “essentiallyfree” of a particular mobile compound means that the compositions of thepresent invention contain less than 100 parts per million (ppm) of therecited mobile compound. The term “essentially completely free” of aparticular mobile compound means that the compositions of the presentinvention contain less than 5 parts per million (ppm) of the recitedmobile compound. The term “completely free” of a particular mobilecompound means that the compositions of the present invention containless than 20 parts per billion (ppb) of the recited mobile compound.

The term “mobile” means that the compound can be extracted from thecured coating when a coating (typically, approximate film weight of 1mg/cm²) is exposed to a test medium for some defined set of conditions,depending on the end use. An example of these testing conditions isexposure of the cured coating to 10 weight percent ethanol solution fortwo hours at 121° C. followed by exposure for 10 days in the solution at49° C.

If the aforementioned phrases are used without the term “mobile” (e.g.,“substantially free of XYZ compound”) then the compositions of thepresent invention contain less than the aforementioned amount of thecompound whether the compound is mobile in the coating or bound to aconstituent of the coating.

As used herein, the term “organic group” means a hydrocarbon group (withoptional elements other than carbon and hydrogen, such as oxygen,nitrogen, sulfur, and silicon) that is classified as an aliphatic group,cyclic group, or combination of aliphatic and cyclic groups (e.g.,alkaryl and aralkyl groups). The term “aliphatic group” means asaturated or unsaturated linear or branched hydrocarbon group. This termis used to encompass alkyl, alkenyl, and alkynyl groups, for example.The term “alkyl group” means a saturated linear or branched hydrocarbongroup including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl,dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term “alkenylgroup” means an unsaturated, linear or branched hydrocarbon group withone or more carbon-carbon double bonds, such as a vinyl group. The term“alkynyl group” means an unsaturated, linear or branched hydrocarbongroup with one or more carbon-carbon triple bonds. The term “cyclicgroup” means a closed ring hydrocarbon group that is classified as analicyclic group or an aromatic group, both of which can includeheteroatoms. The term “alicyclic group” means a cyclic hydrocarbon grouphaving properties resembling those of aliphatic groups.

The term “Ar” refers to a divalent aryl group (i.e., an arylene group),which refers to a closed aromatic ring or ring system such as phenylene,naphthylene, biphenylene, fluorenylene, and indenyl, as well asheteroarylene groups (i.e., a closed ring hydrocarbon in which one ormore of the atoms in the ring is an element other than carbon (e.g.,nitrogen, oxygen, sulfur, etc.)). Suitable heteroaryl groups includefuryl, thienyl, pyridyl, quinolinyl, isoquinolinyl, indolyl, isoindolyl,triazolyl, pyrrolyl, tetrazolyl, imidazolyl, pyrazolyl, oxazolyl,thiazolyl, benzofuranyl, benzothiophenyl, carbazolyl, benzoxazolyl,pyrimidinyl, benzimidazolyl, quinoxalinyl, benzothiazolyl,naphthyridinyl, isoxazolyl, isothiazolyl, purinyl, quinazolinyl,pyrazinyl, 1-oxidopyridyl, pyridazinyl, triazinyl, tetrazinyl,oxadiazolyl, thiadiazolyl, and so on. When such groups are divalent,they are typically referred to as “heteroarylene” groups (e.g.,furylene, pyridylene, etc.)

A group that may be the same or different is referred to as being“independently” something.

Substitution is anticipated on the organic groups of the compounds ofthe present invention. As a means of simplifying the discussion andrecitation of certain terminology used throughout this application, theterms “group” and “moiety” are used to differentiate between chemicalspecies that allow for substitution or that may be substituted and thosethat do not allow or may not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withO, N, Si, or S atoms, for example, in the chain (as in an alkoxy group)as well as carbonyl groups or other conventional substitution. Where theterm “moiety” is used to describe a chemical compound or substituent,only an unsubstituted chemical material is intended to be included. Forexample, the phrase “alkyl group” is intended to include not only pureopen chain saturated hydrocarbon alkyl substituents, such as methyl,ethyl, propyl, t-butyl, and the like, but also alkyl substituentsbearing further substituents known in the art, such as hydroxy, alkoxy,alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus,“alkyl group” includes ether groups, haloalkyls, nitroalkyls,carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On the other hand, thephrase “alkyl moiety” is limited to the inclusion of only pure openchain saturated hydrocarbon alkyl substituents, such as methyl, ethyl,propyl, t-butyl, and the like.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “a” polymer can be interpreted to mean that the coatingcomposition includes “one or more” polymers.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This invention provides a coating composition for use on food andbeverage cans that includes a latex polymer. The polymer is prepared inan emulsion polymerization process, preferably a free radical initiatedpolymerization process. The latex polymer can be applied to a metalsubstrate either before or after the substrate is formed into a food orbeverage can (e.g., two-piece cans, three-piece cans) or portionsthereof, whether it be a can end or can body. The latex polymers of thepresent invention are suitable for use in food contact situations andmay be used on the inside of such cans. They are particularly useful onthe interior of two-piece drawn and ironed beverage cans and on beveragecan ends.

In one embodiment, the latex polymer is prepared by polymerizing anethylenically unsaturated monomer component in an aqueous medium in thepresence of the salt of an acid group- or anhydride group-containingpolymer and an amine, preferably, a tertiary amine The ethylenicallyunsaturated monomer component is preferably a mixture of monomers.Preferably, at least one of the monomers in the mixture is an alpha,beta-ethylenically unsaturated monomer, and preferably at least one ofthe monomers contains an oxirane groups. More preferably, at least oneof the monomers is an oxirane group-containing alpha, beta-ethylenicallyunsaturated monomer.

In another embodiment, the latex polymer is prepared by polymerizing theethylenically unsaturated monomer component in the presence of anaqueous dispersion of a polymer, such as for example, awater-dispersible polyester resin, alkyd resin, polyurethane resin, or acombination thereof. The polymer of the aqueous dispersion can be madewater-dispersible by incorporating non-ionic water-dispersing groups,salt groups (e.g., anionic and/or cationic salt groups), or acombination thereof. As used herein, the term “water-dispersing groups”also encompasses water-solubolizing groups.

The composition may optionally include crosslinkers, fillers, catalysts,dyes, pigments, toners, extenders, lubricants, anticorrosion agents,flow control agents, thixotropic agents, dispersing agents,antioxidants, adhesion promoters, light stabilizers, surfactants,organic solvents, and mixtures thereof as required to provide thedesired film properties.

In one embodiment, the coating composition is prepared by: forming asalt of an acid-functional or anhydride-functional polymer and an amine;dispersing the salt in a carrier that includes water and an optionalorganic solvent to form an aqueous dispersion; optionally removing theorganic solvent, if present, from the aqueous dispersion; combining anethylenically unsaturated monomer component with the aqueous dispersion(preferably, the ethylenically unsaturated monomer component is added tothe aqueous dispersion); and polymerizing the ethylenically unsaturatedmonomer component in the presence of the aqueous dispersion to form anemulsion polymerized latex polymer. In some embodiments, a neutralizingbase other than an amine may be used to form the salt of theacid-functional or anhydride-functional polymer. Moreover, in otherembodiments, a polymer salt including salt groups other than neutralizedacid or anhydride groups may be used.

Preferred compositions are substantially free of mobile bisphenol A(BPA) and aromatic glycidyl ether compounds (e.g., BADGE, BFDGE, andepoxy novalacs), more preferably essentially free of these compounds,even more preferably essentially completely free of these compounds, andmost preferably completely free of these compounds. The coatingcomposition is also preferably substantially free of bound BPA andaromatic glycidyl ether compounds, more preferably essentially free ofthese compounds, most preferably essentially completely free of thesecompounds, and optimally completely free of these compounds.

Preferred emulsion polymerized latex polymers are at least substantially“epoxy-free”, more preferably “epoxy-free.” The term “epoxy-free”, whenused herein in the context of a polymer, refers to a polymer that doesnot include any epoxy backbone segments. Thus, for example, a polymermade from ingredients including an epoxy resin would not be consideredepoxy-free. Similarly, a polymer having backbone segments that are thereaction product of a bisphenol (e.g., bisphenol A, bisphenol F,bisphenol S, 4,4′dihydroxy bisphenol, etc.) and a halohdyrin (e.g.,epichlorohydrin) would not be considered epoxy-free. The coatingcomposition is also preferably at least substantially epoxy-free, morepreferably epoxy-free.

The ethylenically unsaturated monomer component is preferably a mixtureof monomers that is capable of free radical initiated polymerization inaqueous medium. The monomer mixture preferably contains at least oneoxirane functional monomer, and more preferably, at least one oxiranegroup-containing alpha, beta-ethylenically unsaturated monomer.

The monomer mixture preferably contains at least 0.1 wt-%, morepreferably at least 1 wt-%, of an oxirane group-containing monomer,based on the weight of the monomer mixture. Typically, at least 0.1 wt-%of the oxirane group-containing monomer contributes to the stability ofthe latex. Although not intended to be limited by theory, it is believedthat this is because of the reduction in the amount of quaternary saltformation between the oxirane species, acid group-containing polymer,and amine, which can cause coagulation of the latex. In addition, atleast 0.1 wt-% of the oxirane group-containing monomer contributes tocrosslinking in the dispersed particles and during cure, resulting inbetter properties of coating compositions formulated with the polymericlatices.

The monomer mixture preferably contains no greater than 30 wt-%, morepreferably no greater than 20 wt-%, even more preferably no greater than10 wt-%, and optimally no greater than 9 wt-%, of the oxiranegroup-containing monomer, based on the weight of the monomer mixture.Typically, greater than 30 wt-% of the oxirane group-containing monomerin the monomer mixture can contribute to diminished film properties.Although not intended to be limited by theory, it is believed that thisis due to embrittlement caused by an overabundance of crosslinking.

In some embodiments, the monomer mixture does not contain anyoxirane-group containing monomer.

Suitable oxirane-functional monomers include monomers having a reactivecarbon-carbon double bond and an oxirane (i.e., a glycidyl) group.Typically, the monomer is a glycidyl ester of an alpha, beta-unsaturatedacid, or anhydride thereof (i.e., an oxirane group-containing alpha,beta-ethylenically unsaturated monomer). Suitable alpha,beta-unsaturated acids include monocarboxylic acids or dicarboxylicacids. Examples of such carboxylic acids include, but are not limitedto, acrylic acid, methacrylic acid, alpha-chloroacrylic acid,alpha-cyanoacrylic acid, beta-methylacrylic acid (crotonic acid),alpha-phenylacrylic acid, beta-acryloxypropionic acid, sorbic acid,alpha-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamicacid, beta-stearylacrylic acid, itaconic acid, citraconic acid,mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaricacid, tricarboxyethylene, maleic anhydride, and mixtures thereof.

Specific examples of suitable monomers containing a glycidyl group areglycidyl (meth)acrylate (i.e., glycidyl methacrylate and glycidylacrylate), mono- and di-glycidyl itaconate, mono- and di-glycidylmaleate, and mono- and di-glycidyl formate. It also is envisioned thatallyl glycidyl ether and vinyl glycidyl ether can be used as theoxirane-functional monomer. A preferred monomer is glycidyl methacrylate(“GMA”).

The oxirane-functional monomer is preferably reacted with suitable othermonomers within the monomer mixture. These can be ethylenicallyunsaturated monomer and hydroxy-functional monomers. Suitableethylenically unsaturated monomers include alkyl (meth)acrylates, vinylmonomers, alkyl esters of maleic or fumaric acid, and the like.

Suitable alkyl (meth)acrylates include those having the structure:CH₂═C(R¹)—CO—OR² wherein R¹ is hydrogen or methyl, and R² is an alkylgroup preferably containing one to sixteen carbon atoms. The R² groupcan be substituted with one or more, and typically one to three,moieties such as hydroxy, halo, phenyl, and alkoxy, for example.Suitable alkyl (meth)acrylates therefore encompass hydroxy alkyl(meth)acrylates. The alkyl (meth)acrylate typically is an ester ofacrylic or methacrylic acid. Preferably, R¹ is hydrogen or methyl and R²is an alkyl group having two to eight carbon atoms. Most preferably, R¹is hydrogen or methyl and R² is an alkyl group having two to four carbonatoms.

Examples of suitable alkyl (meth)acrylates include, but are not limitedto, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate,pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl(meth)acrylate, isodecyl (meth)acrylate, benzyl (meth)acrylate, lauryl(meth)acrylate, isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl(meth)acrylate, hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate(HEMA), hydroxypropyl (meth)acrylate (HPMA).

Difunctional (meth)acrylate monomers may be used in the monomer mixtureas well. Examples include ethylene glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, allyl methacrylate, and the like.

Suitable vinyl monomers include styrene, methyl styrene, halostyrene,isoprene, diallylphthalate, divinylbenzene, conjugated butadiene,alpha-methylstyrene, vinyl toluene, vinyl naphthalene, and mixturesthereof. The vinyl aromatic monomers described below in connection withthe acid- or anhydride-functional polymer are also suitable for use inthe ethylenically unsaturated monomer component used to make the latexpolymer. Styrene is a presently preferred vinyl monomer, in part due toits relatively low cost.

Other suitable polymerizable vinyl monomers for use in the ethylenicallyunsaturated monomer component include acrylonitrile, acrylamide,methacrylamide, methacrylonitrile, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl stearate, N-isobutoxymethyl acrylamide,N-butoxymethyl acrylamide, and the like.

When present, the oxirane group-containing monomer preferablyconstitutes 0.1 wt-% to 30 wt-%, and more preferably 1 wt-% to 20 wt-%,of the ethylenically unsaturated monomer component. The other monomer ormonomers in the mixture constitute the remainder of the monomercomponent, that is, 70 wt-% to 99.9 wt-%, preferably 80 wt-% to 99 wt-%,based on total weight of the monomer mixture.

Preferably, at least 40 wt-% of the ethylenically unsaturated monomercomponent, more preferably at least 50 wt-%, will be selected from alkylacrylates and methacrylates. Preferably, at least 20 wt-%, morepreferably at least 30 wt-%, will be selected from vinyl aromaticcompounds.

Preferably, at least 5 wt-%, more preferably at least 25 wt-%, even morepreferably at least 50 wt-%, and even more preferably at least 60 wt-%,of the ethylenically unsaturated monomer component is used in making thelatex polymer. Preferably, no greater than 95 wt-%, more preferably nogreater than 90 wt-%, and even more preferably no greater than 85 wt-%,of the ethylenically unsaturated monomer component is used in making thelatex polymer. Such percentages are based on total weight ofethylenically unsaturated monomer component and salt of the acidgroup-containing or anhydride group-containing polymer (i.e.,acid-functional or anhydride-functional polymer)). In embodiments whereother water-dispersible polymers are used in place of or in addition tothe acid group-containing or anhydride group-containing polymer, suchpercentages are based on total weight of ethylenically unsaturatedmonomer component and water-dispersible polymers.

Among the acid functional polymers that can be employed in preparing thelatex polymer of the present invention are virtually any acid-containingor anhydride-containing polymers that can be neutralized or partiallyneutralized with an appropriate amine or other suitable base to form asalt that can be dissolved or stably dispersed in the aqueous medium.The choice of the acid-containing or anhydride-containing monomer(s) isdictated by the intended end use of the coating composition and ispractically unlimited.

The acid-containing polymer (i.e., acid-functional polymer) preferablyhas an acid number of at least 40, and more preferably at least 100,milligrams (mg) KOH per gram resin. The acid-containing polymerpreferably has an acid number of no greater than 400, and morepreferably no greater than 300, mg KOH per gram resin. Theanhydride-containing polymer, when in water, preferably has similar acidnumber ranges.

Low molecular weight polymers are preferred for certain applications ofthe present invention. Preferably, the molecular weight of the acid- oranhydride-functional polymer is no greater than 50,000 on a numberaverage molecular weight basis, and preferably no greater than 20,000.Preferably, the molecular weight of the acid- or anhydride-functionalpolymer is at least 1500 on a number average molecular weight basis, andmore preferably at least 2000. When salt-forming groups other than acid-or anhydride-groups are used, the molecular weight of the polymer saltwill typically fall within the above parameters.

Preferred acid- or anhydride-functional polymers that may be employedinclude acid-functional or anhydride-functional acrylic polymers, alkydresins, polyester polymers, and polyurethanes. Combinations of suchpolymers can be used if desired. Herein, the term polymer includes bothhomopolymers and copolymers (i.e., polymers of two or more differentmonomers).

Preferred acid- or anhydride-functional polymers utilized in thisinvention include those prepared by conventional free radicalpolymerization techniques. Suitable examples include those prepared fromunsaturated acid- or anhydride-functional monomers, or salts thereof,and other unsaturated monomers. Of these, preferred examples includethose prepared from at least 15 wt-%, more preferably at least 20 wt-%,unsaturated acid- or anhydride-functional monomer, or salts thereof, andthe balance other polymerizable unsaturated monomer. Examples ofco-monomers described previously apply here as well.

A variety of acid- or anhydride-functional monomers, or salts thereof,can be used; their selection is dependent on the desired final polymerproperties. Preferably, such monomers are ethylenically unsaturated,more preferably, alpha, beta-ethylenically unsaturated. Suitableethylenically unsaturated acid- or anhydride-functional monomers for thepresent invention include monomers having a reactive carbon-carbondouble bond and an acidic or anhydride group, or salts thereof.Preferred such monomers have from 3 to 20 carbons, at least 1 site ofunsaturation, and at least 1 acid or anhydride group, or salt thereof.

Suitable acid-functional monomers include ethylenically unsaturatedacids (mono-protic or diprotic), anhydrides or monoesters of a dibasicacid, which are copolymerizable with the optional other monomer(s) usedto prepare the polymer.

Illustrative monobasic acids are those represented by the structureCH₂═C(R³)—COOH, where R³ is hydrogen or an alkyl radical of 1 to 6carbon atoms. Suitable dibasic acids are those represented by theformulas R⁴(COOH)C═C(COOH)R⁵ and R⁴(R⁵)C═C(COOH)R⁶COOH, where R⁴ and R⁵are hydrogen, an alkyl radical of 1-8 carbon atoms, halogen, cycloalkylof 3 to 7 carbon atoms or phenyl, and R⁶ is an alkylene radical of 1 to6 carbon atoms. Half-esters of these acids with alkanols of 1 to 8carbon atoms are also suitable.

Non-limiting examples of useful ethylenically unsaturatedacid-functional monomers include acids such as, for example, acrylicacid, methacrylic acid, alpha-chloroacrylic acid, alpha-cyanoacrylicacid, crotonic acid, alpha-phenylacrylic acid, beta-acryloxypropionicacid, fumaric acid, maleic acid, sorbic acid, alpha-chlorosorbic acid,angelic acid, cinnamic acid, p-chlorocinnamic acid, beta-stearylacrylicacid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid,tricarboxyethylene, 2-methyl maleic acid, itaconic acid, 2-methylitaconic acid, methyleneglutaric acid, and the like, or mixturesthereof. Preferred unsaturated acid-functional monomers include acrylicacid, methacrylic acid, crotonic acid, fumaric acid, maleic acid,2-methyl maleic acid, itaconic acid, 2-methyl itaconic acid, andmixtures thereof. More preferred unsaturated acid-functional monomersinclude acrylic acid, methacrylic acid, crotonic acid, fumaric acid,maleic acid, itaconic acid, and mixtures thereof. Most preferredunsaturated acid-functional monomers include acrylic acid, methacrylicacid, maleic acid, crotonic acid, and mixtures thereof.

Nonlimiting examples of suitable ethylenically unsaturated anhydridemonomers include compounds derived from the above acids (e.g., as pureanhydride or mixtures of such). Preferred anhydrides include acrylicanhydride, methacrylic anhydride, and maleic anhydride. If desired,aqueous salts of the above acids may also be employed.

Polymerization of the monomers to form an acid- or anhydride-functionalpolymer is usually conducted by organic solution polymerizationtechniques in the presence of a free radical initiator as is well knownin the art. Although the preparation of the acid-functional oranhydride-functional polymer is conveniently carried out in solution,neat processes may be used if desired.

Besides the acid- or anhydride-functional acrylic polymers, acid- oranhydride-functional alkyd, polyester, polyurethane resins, orcombinations thereof, can also be used in the practice of the invention.Such polymers are described in U.S. Pat. Nos. 4,692,491; 3,479,310; and4,147,679. Preferably, the acid- or anhydride-functional polymers areacid-functional acrylic polymers.

In another preferred embodiment, the acid- or anhydride-functionalpolymers are polyester polymers. Examples of such polyester polymers aredisclosed in U.S. Provisional Patent Application Ser. No. 60/727,734(Attorney Docket No. 287.00220160), filed on, Oct. 18, 2005 entitledCOATING COMPOSITIONS FOR CONTAINERS AND METHODS OF COATING, subsequentlyfiled as U.S. Non-Provisional patent application Ser. No. 11/550,451.Briefly, the polymers described therein have one or more segments ofFormula I:

—O—Ar—R_(n)—C(O)—O—R¹—O—C(O)—R_(n)—Ar—O—

wherein each Ar is independently a divalent aryl group (i.e., an arylenegroup) or heteroarylene group; R¹ is a divalent organic group; each R isindependently a divalent organic group; and n is 0 or 1. Any one polymercan have a variety of such segments, which may be the same or different.

Preferably, R¹ provides hydrolytic stability to at least one of theadjacent ester linkages (—C(O)—O— and —O—C(O)—), and preferably to bothof them. In this context, “hydrolytic stability” means that R¹ decreasesthe reactivity (preferably, by at least half) of the adjacent esterlinkage with water compared to a —CH₂—CH₂— moiety under the sameconditions. This can be accomplished by selection of R¹ that includes asterically bulky group in proximity (preferably within two atomsdistance) to the oxygen of the ester. The polymer preferably includesmore than 70%, more preferably more than 80%, and even more preferablymore than 90%, hydrolytically stable ester linkages (based on the totalnumber of ester linkages).

In the segments of Formula I, R¹ is a divalent organic group,preferably, having at least 3 carbon atoms, more preferably, at least 4carbon atoms, even more preferably, at least 5 carbon atoms, and evenmore preferably, at least 8 carbon atoms. It is envisioned that R¹ canbe as large as desired for the particular application, which one ofskill in the art can readily determine.

In certain preferred embodiments of Formula I, R¹ is of the formula

—C(R²)₂—Y_(t)—C(R²)₂—

wherein each R² is independently hydrogen or an organic group (e.g., analicyclic group or a branched or unbranched alkyl group), Y is adivalent organic group, and t is 0 or 1 (preferably 1). In certainembodiments, each R² is independently hydrogen.

In certain embodiments, Y can optionally include one or more ether orester linkages. In certain embodiments, Y is a divalent saturatedaliphatic group (i.e., a branched or unbranched alkylene group), adivalent alicyclic group, or a divalent aromatic group (i.e., an arylenegroup), or combinations thereof.

In certain embodiments, Y is a divalent alkyl group (i.e., an alkylenegroup), which can be branched or unbranched, preferably having at least1 carbon atom, more preferably having at least 2 carbon atoms, even morepreferably having at least 3 carbon atoms, and even more preferablyhaving at least 6 carbon atoms. In certain embodiments, Y is a divalentalicylic group, preferably cyclohexylene. It is envisioned that Y can beas large as desired for the particular application, which one of skillin the art can readily determine

Preferably, Y provides hydrolytic stability to at least one of the esterlinkages adjacent R¹ in Formula I. This can be accomplished by selectionof Y that includes a sterically bulky group that is in proximity(preferably within two atoms) of at least one of the ester oxygen atomsin Formula I.

In certain embodiments, R¹ has the formula —(C(R²)₂)_(s)— wherein s isat least 2, and preferably, s is at least 3, wherein each R² is asdefined above. Examples of such R¹ groups include, for example,neopentylene, butylethylpropylene, and —CH₂—CH(CH₃)—CH₂—.

In certain embodiments, Y has the formula

—[Z_(w)—C(R²)₂—O—C(O)—R³—C(O)—O—C(R²)₂—]_(v)Z_(w)—,

wherein w is 0 or 1, v is 1 to 10, each R² is as defined above, each R³is independently a divalent organic group, and each Z is independently adivalent organic group.

In certain embodiments, R³ is a divalent saturated aliphatic group(i.e., branched or unbranched alkylene group), a divalent alicyclicgroup, an arylene group, or combinations thereof. In certainembodiments, R³ is a (C3-C20)alkylene (branched or unbranched) group ora phenylene group.

In certain embodiments, Z is a divalent saturated aliphatic group (i.e.,branched or unbranched alkylene group), a divalent alicyclic group, adivalent aromatic group (i.e., an arylene group), or combinationsthereof.

Preferably, Z provides hydrolytic stability to at least one of the esterlinkages adjacent R¹ in Formula I and/or to an adjacent ester linkagecontained within Y. This can be accomplished by selection of Z thatincludes a sterically bulky group that is in proximity (preferablywithin two atoms distance) of at least one of the ester oxygen atoms.

In the segments of Formula I, n is preferably 0 (i.e., R is notpresent). If n is 1 and R is present, however, it is preferably a(C1-C4)alkylene group, and more preferably a (C1-C4)alkylene moiety.

In the segments of Formula I, preferably each Ar has less than 20 carbonatoms, more preferably less than 11 carbon atoms, and even morepreferably less than 8 carbon atoms. Preferably, Ar has at least 4carbon atoms, more preferably at least 5 carbon atoms, and even morepreferably, at least 6 carbon atoms.

In certain embodiments, each Ar is a phenylene group. In certainembodiments, each Ar is a phenylene group of the formula —C₆(R⁴)₄—,wherein each R⁴ is independently hydrogen, a halogen, or an organicgroup, and wherein two R⁴ groups can join to form a ring optionallycontaining one or more heteroatoms. In certain embodiments, R⁴ ishydrogen or an organic group, wherein two R⁴ groups can join to form a6-membered ring. Preferably, R⁴ is hydrogen.

Polyester polymers such as these can be made by a variety of methodsfrom compounds of Formula II:

HO—Ar—R_(n)—C(O)—O—R¹—O—C(O)—R_(n)—Ar—OH

wherein Ar, R, R¹, and n are as defined above. Such compounds can bemade, for example, by the esterification reaction of one mole of a diol(e.g., HO—R¹—OH such as, for example, 1,4-cyclohexane dimethanol,neopentyl glycol, 2-butyl-2-ethyl-1,3-propane diol, or2-methyl-1,3-propane diol) with two moles of an acid (e.g., 4-hydroxybenzoic acid). Alternatively, such compounds can be made, for example,by the transesterification reaction of one mole of a diol (e.g.,1,4-cyclohexane dimethanol, neopentyl glycol,2-butyl-2-ethyl-1,3-propane diol, or 2-methyl-1,3-propane diol) with twomoles of an ester (e.g., 4-hydroxy methyl benzoate, 4-hydroxy ethylbenzoate, or 4-hydroxy butyl benzoate).

Polymers of Formula I can be prepared by methods that involve advancingthe molecular weight of compounds of Formula II. In certain embodiments,compounds of Formula II (e.g., dihydric phenols) can be reacted with adiepoxide to advance the molecular weight. For example, compounds ofFormula II (e.g., dihydric phenols) can be reacted with non-BPA andnon-BPF based diepoxides much in the same manner that Bisphenol A orBisphenol F do, to create polymers that can be formulated withcrosslinkers and additives for coatings for rigid packaging. Forexample, compounds of Formula II can be reacted with a diepoxide to forma polymer that includes —CH₂—CH(OH)—CH₂— segments. Alternatively,compounds of Formula II can be reacted with epichlorohydrin to form adiepoxide analog of compounds of Formula II, which can then be reactedwith other compounds of Formula II to form a polymer that includes—CH₂—CH(OH)—CH₂— segments.

The diepoxide analogs of compounds of Formula II (e.g., glycidylpolyethers of the dihydric phenols) can be prepared by reacting therequired proportions of a compound of Formula II (e.g., dihydric phenol)and epichlorohydrin in an alkaline medium. The desired alkalinity isobtained by adding basic substances, such as sodium or potassiumhydroxide, preferably in stoichiometric excess to the epichlorohydrin.The reaction is preferably accomplished at temperatures of 50° C. to150° C. The heating is continued for several hours to effect thereaction and the product is then washed free of salt and base.Procedures for such reactions are generally well known and disclosed,for example, in U.S. Pat. No. 2,633,458.

As used in the present invention, suitable diepoxides (other than thediepoxide analogs of compounds of Formula II) are BPA- or BPF-freediepoxides, preferably with one or more ether linkages. Suitablediepoxides may be prepared by a variety of processes, for example, bythe condensation of a dihydroxy compound and epichlorohydrin. Examplesof suitable diepoxides (other than the diepoxide analogs of compounds ofFormula II) include, for example, 1,4-cyclohexanedimethanol diglycidylether (CHDMDGE), resorcinol diglycidyl ether, neopentyl glycoldiglycidyl ether, and 2-methyl-1,3-propandiol diglycidyl ether.

The resultant polymers of Formula I may be epoxy terminated or phenoxyterminated, for example. They may be made in a variety of molecularweights, such as the molecular weights of commercially availableBPA-based epoxy materials (e.g., those available under tradedesignations such as EPON 828, 1001, 1007, 1009 from ResolutionPerformance Products, Houston, Tex.). Preferred polymers of the presentinvention have a number average molecular weight (Mn) of at least 2,000,more preferably at least 3,000, and even more preferably at least 4,000.The molecular weight of the polymer may be as high as is needed for thedesired application.

Advancement of the molecular weight of the polymer may be enhanced bythe use of a catalyst in the reaction of a diepoxide (whether it be adiepoxide analog of Formula II or another diepoxide) with a compound ofFormula (II). Typical catalysts usable in the advancement of themolecular weight of the epoxy material of the present invention includeamines, hydroxides (e.g., potassium hydroxide), phosphonium salts, andthe like. A presently preferred catalyst is a phosphonium catalyst. Thephosphonium catalyst useful in the present invention is preferablypresent in an amount sufficient to facilitate the desired condensationreaction.

Alternatively, the epoxy terminated polymers of Formula I may be reactedwith fatty acids to form polymers having unsaturated (e.g., airoxidizable) reactive groups, or with acrylic acid or methacrylic acid toform free radically curable polymers.

Advancement of the molecular weight of the polymer may also be enhancedby the reaction of an epoxy terminated polymer of Formula I with asuitable diacid (such as adipic acid).

A salt (which can be a full salt or partial salt) of the acid- oranhydride-functional polymer is formed by neutralizing or partiallyneutralizing the acid groups (whether present initially in theacid-functional polymer or formed upon addition of theanhydride-functional polymer to water) of the polymer with a suitablebase such as, for example, an amine, preferably a tertiary amine Someexamples of suitable tertiary amines are trimethyl amine,dimethylethanol amine (also known as dimethylamino ethanol),methyldiethanol amine, triethanol amine, ethyl methyl ethanol amine,dimethyl ethyl amine, dimethyl propyl amine, dimethyl 3-hydroxy-1-propylamine, dimethylbenzyl amine, dimethyl 2-hydroxy-1-propyl amine, diethylmethyl amine, dimethyl 1-hydroxy-2-propyl amine, triethyl amine,tributyl amine, N-methyl morpholine, and mixtures thereof. Mostpreferably triethyl amine or dimethyl ethanol amine is used as thetertiary amine.

The degree of neutralization required to form the desired polymer saltmay vary considerably depending upon the amount of acid included in thepolymer, and the degree of solubility or dispersibility of the saltwhich is desired. Ordinarily in making the polymer water-dispersible,the acidity of the polymer is at least 25% neutralized, preferably atleast 30% neutralized, and more preferably at least 35% neutralized,with the amine in water.

When using anionic salt-forming groups other than acid or anhydridegroups or cationic salt-forming groups, the degree of neutralization maybe pursuant to those described above. Preferably, the polymer of theaqueous dispersion includes a sufficient number of water-dispersinggroups to form a stable aqueous dispersion.

As previously discussed, any suitable salt-forming or water-dispersinggroup may be used in place of, or in addition to, acid or anhydridegroups. For further discussion of such groups, see, for example, U.S.Pat. No. 4,147,679. Some further examples of anionic salt groups includesulphate groups (—OSO₃ ⁻), phosphate groups (—OPO₃ ⁻), sulfonate groups(—SO₂O⁻), phosphinate groups (—POO⁻), phosphonate groups (—PO₃ ⁻), andcombinations thereof. Some examples of suitable cationic salt groupsinclude:

(referred to, respectively, as quaternary ammonium groups, quaternaryphosphonium groups, and tertiary sulfate groups) and combinationsthereof. Some examples of non-ionic water-dispersing groups includehydrophilic groups such as ethylene oxide groups. Compounds forintroducing the aforementioned groups into polymers are known in theart. Some additional examples of neutralizing bases for forming anionicsalt groups include inorganic and organic bases such as sodiumhydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide,and mixtures thereof. Some examples of neutralizing compounds forforming cationic salt groups include organic and inorganic acids such asformic acid, acetic acid, hydrochloric acid, sulfuric acid, andcombinations thereof.

The amount of the salt of the acid-functional or anhydride-functionalpolymer that is used in the polymerization is preferably at least 5wt-%, more preferably at least 10 wt-%, and even more preferably atleast 15 wt-%. The amount of the salt of the acid-functional oranhydride-functional polymer that is used in the polymerization ispreferably no greater than 95 wt-%, preferably no greater than 50 wt-%,and even more preferably no greater than 40 wt-%. These percentages arebased on total weight of polymerizable ethylenically unsaturated monomercomponent and the salt of the acid group-containing polymer. Inembodiments where the polymer includes water-dispersing groups otherthan neutralized acid- or anhydride-groups, the total amount of thepolymer used in the polymerization will typically fall within the aboveparameters, with the above percentages based on based on total weight ofethylenically unsaturated monomer component and water-dispersiblepolymers

The reaction of tertiary amines with materials containing oxiranegroups, when carried out in the presence of water, can afford a productthat contains both a hydroxyl group and a quaternary ammonium hydroxide.Under preferred conditions an acid group, an oxirane group, and an amineform a quaternary salt. This linkage is favored, as it not only linksthe polymers but promotes water dispersibility of the joined polymer. Itshould be noted that an acid group and an oxirane group may also form anester. Some of this reaction is possible, though this linkage is lessdesirable when water dispersibility is sought.

While the exact mode of reaction is not fully understood, it is believedthat a competition between the two reactions exist; however, this is notintended to be limiting. In preferred embodiments, one reaction involvesthe tertiary amine neutralized acid-functional polymer reacting with anoxirane-functional monomer or polymer to form a quaternary ammoniumsalt. A second reaction involves esterification of theoxirane-functional monomer or polymer with a carboxylic acid or salt. Inthe current invention it is believed the presence of water and level ofamine favor formation of quaternary ammonium salts over ester linkages.A high level of quaternization improves water dispersability while ahigh level of esterification gives higher viscosity and possiblygel-like material.

With regard to the conditions of the emulsion polymerization, theethylenically unsaturated monomer component is preferably polymerized inaqueous medium with a water-soluble free radical initiator in thepresence of the salt of the acid- or anhydride-functional polymer.

The temperature of polymerization is typically from 0° C. to 100° C.,preferably from 50° C. to 90° C., more preferably from 70° C. to 90° C.,and even more preferably from 80° C. to 85° C. The pH of the aqueousmedium is usually maintained at a pH of 5 to 12.

The free radical initiator can be selected from one or morewater-soluble peroxides which are known to act as free radicalinitiators. Examples include hydrogen peroxide and t-butylhydroperoxide. Redox initiator systems well known in the art (e.g.,t-butyl hydroperoxide, erythorbic acid, and ferrous complexes) can alsobe employed. In some embodiments, it is especially preferred to use amixture of benzoin and hydrogen peroxide. Persulfate initiators such asammonium persulfate or potassium persulfate are not preferred, as theylead to poor water resistance properties of the cured coating.

Further examples of polymerization initiators which can be employedinclude polymerization initiators which thermally decompose at thepolymerization temperature to generate free radicals. Examples includeboth water-soluble and water-insoluble species. Further examples of freeradical initiators that can be used include persulfates, such asammonium or alkali metal (potassium, sodium or lithium) persulfate; azocompounds such as 2,2′-azo-bis(isobutyronitrile),2,2′-azo-bis(2,4-dimethylvaleronitrile), and1-t-butyl-azocyanocyclohexane; hydroperoxides such as t-butylhydroperoxide, hydrogen peroxide, t-amyl hydroperoxide, methylhydroperoxide, and cumene hydroperoxide; peroxides such as benzoylperoxide, caprylyl peroxide, di-t-butyl peroxide, ethyl3,3′-di(t-butylperoxy) butyrate, ethyl 3,3′-di(t-amylperoxy) butyrate,t-amylperoxy-2-ethyl hexanoate, and t-butylperoxy pivilate; peresterssuch as t-butyl peracetate, t-butyl perphthalate, and t-butylperbenzoate; as well as percarbonates, such asdi(1-cyano-1-methylethyl)peroxy dicarbonate; perphosphates, and thelike; and combinations thereof.

Polymerization initiators can be used alone or as the oxidizingcomponent of a redox system, which also preferably includes a reducingcomponent such as ascorbic acid, malic acid, glycolic acid, oxalic acid,lactic acid, thiogycolic acid, or an alkali metal sulfite, morespecifically a hydrosulfite, hyposulfite or metabisulfite, such assodium hydrosulfite, potassium hyposulfite and potassium metabisulfite,or sodium formaldehyde sulfoxylate, and combinations thereof. Thereducing component is frequently referred to as an accelerator or acatalyst activator.

The initiator and accelerator is preferably used in proportion fromabout 0.001% to 5% each, based on the weight of monomers to becopolymerized. Promoters such as chloride and sulfate salts of cobalt,iron, nickel or copper can be used in small amounts, if desired.Examples of redox catalyst systems include tert-butylhydroperoxide/sodium formaldehyde sulfoxylate/Fe(II), and ammoniumpersulfate/sodium bisulfate/sodium hydrosulfite/Fe(II).

Chain transfer agents can be used to control polymer molecular weight,if desired.

The polymerization reaction of the ethylenically unsaturated monomercomponent in the presence of the aqueous dispersion of the polymer saltmay be conducted as a batch, intermittent, or continuous operation.While all of the polymerization ingredients may be charged initially tothe polymerization vessel, better results normally are obtained withproportioning techniques. In certain embodiments, however, it isdesirable to charge all, or substantially all, of the ingredients to thepolymerization vessel before commencing polymerization.

Typically, the reactor is charged with an appropriate amount of water,polymer salt, and free radical initiator. The reactor is then heated tothe free radical initiation temperature and then charged with theethylenically unsaturated monomer component. Preferably only water,initiator, polymer salt, and some portion of the ethylenicallyunsaturated monomer component are initially charged to the vessel. Theremay also be some water miscible solvent present. After this initialcharge is allowed to react for a period of time at polymerizationtemperature, the remaining ethylenically unsaturated monomer componentis added incrementally with the rate of addition being varied dependingon the polymerization temperature, the particular initiator beingemployed, and the type and amount of monomers being polymerized. Afterall the monomer component has been charged, a final heating is carriedout to complete the polymerization. The reactor is then cooled and thelatex recovered.

As discussed above, in certain embodiments a “batch” process may be usedto polymerize the ethylenically unsaturated monomer component in thepresence of the aqueous dispersion. While not intending to be bound byany theory, batch polymerization of the ethylenically unsaturatedmonomer component can result in a higher molecular weight polymerizedcomponent that may yield desirable performance properties for certaincoating end uses such as, for example, beverage end coatings. In certainpreferred embodiments, the polymerized ethylenically unsaturated monomercomponent has a Mn of at least about 100,000, more preferably at leastabout 200,000, or even more preferably at least about 300,000. The upperrange of the Mn of the polymerized ethylenically unsaturated monomercomponent is not restricted and may be 1,000,000 or more. In certainembodiments, however, the Mn of the polymerized ethylenicallyunsaturated component is less than about 1,000,000, or less than about600,000.

Redox initiation is presently preferred for use in batch polymerizingthe ethylenically unsaturated component.

It is contemplated that the benefits of a batch polymerization processmay also be realized by (i) batch polymerizing, for example, asubstantial portion (e.g., at least a majority) of the ethylenciallyunsaturated monomer component and then later (ii) adding the balance ofthe ethylenically unsaturated monomer component (e.g., through acontinuous or intermittent feed) and completing the polymerization.Thus, for example, in certain embodiments, at least about 75 wt-%, morepreferably at least about 85 wt-%, and even more preferably at leastabout 95 wt-% of the total amount of ethylenically unsaturated monomercomponent is present as unreacted monomer in the aqueous dispersionwithin a 1-hour time period (more preferably within a 30-minute timeperiod) during polymerization of the ethylenically unsaturated monomercomponent, and more preferably at the same time (e.g., at the onset ofpolymerization of the ethylenically unsaturated monomer component).

In some embodiments (e.g., where batch polymerization is used), thepolymerized ethylenically unsaturated monomer component constitutes atleast about 75 wt-% of the emulsion polymerized latex polymer, morepreferably at least about 85 wt-%, and even more preferably at leastabout 95 wt-%.

In some embodiments (e.g., where batch polymerization is used), theemulsion polymerized latex polymer exihibts a Mn of at least about100,000, more preferably at least about 200,000, and even morepreferably at least about 300,000.

Coating compositions of the invention preferably include at least afilm-forming amount of the latex polymer. In preferred embodiments, thecoating composition includes at least about 5 wt-%, more preferably atleast about 15 wt-%, and even more preferably at least about 25 wt-% ofthe latex polymer, based on the weight of the latex polymer solidsrelative to the total weight of the coating composition. Preferably, thecoating composition includes less than about 65 wt-%, more preferablyless than about 55 wt-%, and even more preferably less than about 45wt-% of the latex polymer, based on the weight of the latex polymersolids relative to the total weight of the coating composition.

It has been discovered that coating compositions using theaforementioned latices may be formulated using one or more optionalcuring agents (i.e., crosslinking resins, sometimes referred to as“crosslinkers”). The choice of particular crosslinker typically dependson the particular product being formulated. For example, some coatingcompositions are highly colored (e.g., gold-colored coatings). Thesecoatings may typically be formulated using crosslinkers that themselvestend to have a yellowish color. In contrast, white coatings aregenerally formulated using non-yellowing crosslinkers, or only a smallamount of a yellowing crosslinker. Preferred curing agents aresubstantially free of mobile BPA and aromatic glycidyl ether compounds(e.g., BADGE, BFDGE and epoxy novalacs).

Any of the well known hydroxyl-reactive curing resins can be used. Forexample, phenoplast, and aminoplast curing agents may be used.

Phenoplast resins include the condensation products of aldehydes withphenols. Formaldehyde and acetaldehyde are preferred aldehydes. Variousphenols can be employed such as phenol, cresol, p-phenylphenol,p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol.

Aminoplast resins are the condensation products of aldehydes such asformaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with aminoor amido group-containing substances such as urea, melamine, andbenzoguanamine.

Examples of suitable crosslinking resins include, without limitation,benzoguanamine-formaldehyde resins, melamine-formaldehyde resins,esterified melamine-formaldehyde, and urea-formaldehyde resins.Preferably, the crosslinker employed when practicing this inventionincludes a melamine-formaldehyde resin. One specific example of aparticularly useful crosslinker is the fully alkylatedmelamine-formaldehyde resin commercially available from CytecIndustries, Inc. under the trade name of CYMEL 303.

As examples of other generally suitable curing agents are the blocked ornon-blocked aliphatic, cycloaliphatic or aromatic di-, tri-, orpoly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate, and the like. Further examples of generallysuitable blocked isocyanates include isomers of isophorone diisocyanate,dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethanediisocyanate, phenylene diisocyanate, tetramethyl xylene diisocyanate,xylylene diisocyanate, and mixtures thereof. In some embodiments,blocked isocyanates are used that have a Mn of at least about 300, morepreferably at least about 650, and even more preferably at least about1,000.

Polymeric blocked isocyanates are preferred in certain embodiments. Someexamples of suitable polymeric blocked isocyanates include a biuret orisocyanurate of a diisocyanate, a trifunctional “trimer”, or a mixturethereof. Examples of suitable blocked polymeric isocyanates includeTrixene BI 7951, Trixene BI 7984, Trixene BI 7963, Trixene BI 7981(Trixene materials are available from Baxenden Chemicals, Ltd.,Accrington, Lancashire, England), Desmodur BL 3175A, Desmodur BL3272,Desmodur BL3370, Desmodur BL 3475, Desmodur BL 4265, Desmodur PL 340,Desmodur VP LS 2078, Desmodur VP LS 2117, and Desmodur VP LS 2352(Desmodur materials are available from Bayer Corp., Pittsburgh, Pa.,USA), or combinations thereof. Examples of suitable trimers may includea trimerization product prepared from on average three diisocyanatemolecules or a trimer prepared from on average three moles ofdiisocyanate (e.g., HMDI) reacted with one mole of another compound suchas, for example, a triol (e.g., trimethylolpropane).

Examples of suitable blocking agents include malonates, such as ethylmalonate and diisopropyl malonte, acetylacetone, ethyl acetoacetate,1-phenyl-3-methyl-5-pyrazolone, pyrazole, 3-methyl pyrazole, 3,5dimethyl pyrazole, hydroxylamine, thiophenol, caprolactam, pyrocatechol,propyl mercaptan, N-methyl aniline, amines such as diphenyl amine anddiisopropyl amine, phenol, 2,4-diisobutylphenol, methyl ethyl ketoxime,.alpha.-pyrrolidone, alcohols such as methanol, ethanol, butanol andt-butyl alcohol, ethylene imine, propylene imine, benzotriazoles such asbenzotriazole, 5-methylbenzotriazole, 6-ethylbenzotriazole,5-chlorobenzotriazole, and 5-nitrobenzotriazole, methyl ethyl ketoxime(MEKO), diisopropylamine (DIPA), and combinations thereof.

The level of curing agent (i.e., crosslinker) required will depend onthe type of curing agent, the time and temperature of the bake, and themolecular weight of the polymer. If used, the crosslinker is typicallypresent in an amount of up to 50 wt-%, preferably up to 30 wt-%, andmore preferably up to 15 wt-%. If used, the crosslinker is typicallypresent in an amount of at least 0.1 wt-%, more preferably at least 1wt-%, and even more preferably at least 1.5 wt-%. These weightpercentages are based upon the total weight of the resin solids in thecoating composition.

In some embodiments, the coating composition of the invention, based ontotal resin solids, includes at least 5 wt-% of blocked polymericisocyanates, more preferably from about 5 to about 20 wt-% of blockedpolymeric isocyanates, and even more preferably from about 10 to about15 wt-% of blocked polymeric isocyanates.

A coating composition of the present invention may also include otheroptional polymers that do not adversely affect the coating compositionor a cured coating composition resulting therefrom. Such optionalpolymers are typically included in a coating composition as a fillermaterial, although they can be included as a crosslinking material, orto provide desirable properties. One or more optional polymers (e.g.,filler polymers) can be included in a sufficient amount to serve anintended purpose, but not in such an amount to adversely affect acoating composition or a cured coating composition resulting therefrom.

Such additional polymeric materials can be nonreactive, and hence,simply function as fillers. Such optional nonreactive filler polymersinclude, for example, polyesters, acrylics, polyamides, polyethers, andnovalacs. Alternatively, such additional polymeric materials or monomerscan be reactive with other components of the composition (e.g., theacid-functional polymer). If desired, reactive polymers can beincorporated into the compositions of the present invention, to provideadditional functionality for various purposes, including crosslinking.Examples of such reactive polymers include, for example, functionalizedpolyesters, acrylics, polyamides, and polyethers. Preferred optionalpolymers are substantially free of mobile BPA and aromatic glycidylether compounds (e.g., BADGE, BFDGE and epoxy novalacs).

A coating composition of the present invention may also include otheroptional ingredients that do not adversely affect the coatingcomposition or a cured coating composition resulting therefrom. Suchoptional ingredients are typically included in a coating composition toenhance composition esthetics, to facilitate manufacturing, processing,handling, and application of the composition, and to further improve aparticular functional property of a coating composition or a curedcoating composition resulting therefrom.

Such optional ingredients include, for example, catalysts, dyes,pigments, toners, extenders, fillers, lubricants, anticorrosion agents,flow control agents, thixotropic agents, dispersing agents,antioxidants, adhesion promoters, light stabilizers, surfactants, andmixtures thereof. Each optional ingredient is included in a sufficientamount to serve its intended purpose, but not in such an amount toadversely affect a coating composition or a cured coating compositionresulting therefrom.

One preferred optional ingredient is a catalyst to increase the rate ofcure. Examples of catalysts, include, but are not limited to, strongacids (e.g., dodecylbenzene sulphonic acid (DDBSA, available as CYCAT600 from Cytec), methane sulfonic acid (MSA), p-toluene sulfonic acid(pTSA), dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, and tin and zinccompounds. Specific examples include, but are not limited to, atetraalkyl ammonium halide, a tetraalkyl or tetraaryl phosphonium iodideor acetate, tin octoate, zinc octoate, triphenylphosphine, and similarcatalysts known to persons skilled in the art. If used, a catalyst ispreferably present in an amount of at least 0.01 wt-%, and morepreferably at least 0.1 wt-%, based on the weight of nonvolatilematerial. If used, a catalyst is preferably present in an amount of nogreater than 3 wt-%, and more preferably no greater than 1 wt-%, basedon the weight of nonvolatile material.

Another useful optional ingredient is a lubricant (e.g., a wax), whichfacilitates manufacture of metal closures by imparting lubricity tosheets of coated metal substrate. Preferred lubricants include, forexample, Carnauba wax and polyethylene type lubricants. If used, alubricant is preferably present in the coating composition in an amountof at least 0.1 wt-%, and preferably no greater than 2 wt-%, and morepreferably no greater than 1 wt-%, based on the weight of nonvolatilematerial.

Another useful optional ingredient is a pigment, such as titaniumdioxide. If used, a pigment is present in the coating composition in anamount of no greater than 70 wt-%, more preferably no greater than 50wt-%, and even more preferably no greater than 40 wt-%, based on thetotal weight of solids in the coating composition.

Surfactants can be optionally added to the coating composition to aid inflow and wetting of the substrate. Examples of surfactants, include, butare not limited to, nonylphenol polyethers and salts and similarsurfactants known to persons skilled in the art. If used, a surfactantis preferably present in an amount of at least 0.01 wt-%, and morepreferably at least 0.1 wt-%, based on the weight of resin solids. Ifused, a surfactant is preferably present in an amount no greater than 10wt-%, and more preferably no greater than 5 wt-%, based on the weight ofresin solids.

As previously discussed, the coating composition of the inventionpreferably includes water and may further include one or more optionalorganic solvents. Preferably, the coating composition includes at leastabout 20 wt-%, more preferably at least about 25 wt-%, and even morepreferably at least about 30 wt-% of water, based on the weight of thecoating composition. In some embodiments, the coating compositionincludes less than about 60 wt-%, more preferably less than about 50wt-%, and even more preferably less than about 40 wt-% of water, basedon the weight of the coating composition.

In certain embodiments, such as example certain coil coatingapplications, the coating composition preferably includes one or moreorganic solvents in an amount of at least about 10 wt-%, more preferablyat least about 20, and even more preferably at least about 25 wt-%,based on the weight of the coating composition. In some embodiments, thecoating composition includes less than about 70 wt-%, more preferablyless than about 60 wt-%, and even more preferably less than about 45wt-% of organic solvent, based on the weight of the coating composition.While not intending to be bound by any theory, the inclusion of asuitable amount of organic solvent is advantageous for certain coilcoating applications to modify flow and leveling of the coatingcomposition, control blistering, and maximize the line speed of the coilcoater. Moreover, vapors generated from evaporation of the organicsolvent during cure of the coating may be used to fuel the curing ovens.

The coating composition preferably has a total solids content of fromabout 10 to about 70 wt-%, more preferably from about 20 to about 50wt-%, and even more preferably from about 30 to about 40 wt-%, based onthe weight of the coating composition.

In one embodiment, the coating composition includes 5-65 wt-% of thelatex polymer (more preferably 15-55 wt-%, even more preferably 25-45wt-%), 20-60 wt-% of water (more preferably 25-50 wt-%, even morepreferably 30-40 wt-%), and 10-70 wt-% of organic solvent (morepreferably 20-60 wt-%, even more preferably 25-45 wt-%).

As described above, the coating compositions of the present inventionare particularly well adapted for use on food and beverage cans (e.g.,two-piece cans, three-piece cans, etc.). Two-piece cans are manufacturedby joining a can body (typically a drawn metal body) with a can end(typically a drawn metal end). The coatings of the present invention aresuitable for use in food or beverage contact situations and may be usedon the inside of such cans. They are particularly suitable for sprayapplied, liquid coatings for the interior of two-piece drawn and ironedbeverage cans and coil coatings for beverage can ends. The presentinvention also offers utility in other applications. These additionalapplications include, but are not limited to, wash coating, sheetcoating, and side seam coatings (e.g., food can side seam coatings). Thecoating composition may also be useful in medical packagingapplications, including, for example, on surfaces of metered-doseinhalers (“MDIs”), including on drug-contact surfaces.

Spray coating includes the introduction of the coated composition intothe inside of a preformed packaging container. Typical preformedpackaging containers suitable for spray coating include food cans, beerand beverage containers, and the like. The spray preferably utilizes aspray nozzle capable of uniformly coating the inside of the preformedpackaging container. The sprayed preformed container is then subjectedto heat to remove the residual solvents and harden the coating.

A coil coating is described as the coating of a continuous coil composedof a metal (e.g., steel or aluminum). Once coated, the coating coil issubjected to a short thermal, ultraviolet, and/or electromagnetic curingcycle, for hardening (e.g., drying and curing) of the coating. Coilcoatings provide coated metal (e.g., steel and/or aluminum) substratesthat can be fabricated into formed articles, such as two-piece drawnfood cans, three-piece food cans, food can ends, drawn and ironed cans,beverage can ends, and the like.

A wash coating is commercially described as the coating of the exteriorof two-piece drawn and ironed (“D&I”) cans with a thin layer ofprotectant coating. The exterior of these D&I cans are “wash-coated” bypassing pre-formed two-piece D&I cans under a curtain of a coatingcomposition. The cans are inverted, that is, the open end of the can isin the “down” position when passing through the curtain. This curtain ofcoating composition takes on a “waterfall-like” appearance. Once thesecans pass under this curtain of coating composition, the liquid coatingmaterial effectively coats the exterior of each can. Excess coating isremoved through the use of an “air knife.” Once the desired amount ofcoating is applied to the exterior of each can, each can is passedthrough a thermal, ultraviolet, and/or electromagnetic curing oven toharden (e.g., dry and cure) the coating. The residence time of thecoated can within the confines of the curing oven is typically from 1minute to 5 minutes. The curing temperature within this oven willtypically range from 150° C. to 220° C.

A sheet coating is described as the coating of separate pieces of avariety of materials (e.g., steel or aluminum) that have been pre-cutinto square or rectangular “sheets.” Typical dimensions of these sheetsare approximately one square meter. Once coated, each sheet is cured.Once hardened (e.g., dried and cured), the sheets of the coatedsubstrate are collected and prepared for subsequent fabrication. Sheetcoatings provide coated metal (e.g., steel or aluminum) substrate thatcan be successfully fabricated into formed articles, such as two-piecedrawn food cans, three-piece food cans, food can ends, drawn and ironedcans, beverage can ends, and the like.

A side seam coating is described as the spray application of a liquidcoating over the welded area of formed three-piece food cans. Whenthree-piece food cans are being prepared, a rectangular piece of coatedsubstrate is formed into a cylinder. The formation of the cylinder isrendered permanent due to the welding of each side of the rectangle viathermal welding. Once welded, each can typically requires a layer ofliquid coating, which protects the exposed “weld” from subsequentcorrosion or other effects to the contained foodstuff The liquidcoatings that function in this role are termed “side seam stripes.”Typical side seam stripes are spray applied and cured quickly viaresidual heat from the welding operation in addition to a small thermal,ultraviolet, and/or electromagnetic oven.

Other commercial coating application and curing methods are alsoenvisioned, for example, electrocoating, extrusion coating, laminating,powder coating, and the like.

Preferred coatings of the present invention display one or more of theproperties described in the Examples Section. More preferred coatings ofthe present invention display one or more of the following properties:metal exposure value of less than 3 mA; metal exposure value after dropdamage of less than 3.5 mA; global extraction results of less than 50ppm; adhesion rating of 10; blush rating of at least 7; slight or nocrazing in a reverse impact test; no craze (rating of 10) in a domeimpact test; feathering below 0.2 inch; COF range of 0.055 to 0.095; aninitial end continuity of less than 10 mA (more preferably less than 5,2, or 1 mA); and after pasteurization or retort, a continuity of lessthan 20 mA.

EXAMPLES

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight.

Curing Conditions

For beverage inside spray bakes, the curing conditions involvemaintaining the temperature measured at the can dome at 188° C. to 199°C. for 30 seconds.

For beverage end coil bakes, the curing conditions involve the use of atemperature sufficient to provide a peak metal temperature within thespecified time (e.g., 10 seconds at 204° C. means 10 seconds, in theoven, for example, and a peak metal temperature achieved of 204° C.).

The constructions cited were evaluated by tests as follows.

Initial Metal Exposure

This test method determines the amount of the inside surface of the canthat has not been effectively coated by the sprayed coating. Thisdetermination is made thorough the use of an electrically conductivesolution (1% NaCl in deionized water). The coated can is filled withthis room-temperature conductive solution, and an electrical probe isattached in contact to the outside of the can (uncoated, electricallyconducting). A second probe is immersed in the salt solution in themiddle of the inside of the can. If any uncoated metal is present on theinside of the can, a current is passed between these two probes andregisters as a value on an LED display. The LED displays the conveyedcurrents in milliamps (mA). The current that is passed is directlyproportional to the amount of metal that has not been effectivelycovered with coating. The goal is to achieve 100% coating coverage onthe inside of the can, which would result in an LED reading of 0.0 mA.Preferred coatings give metal exposure values of less than 3 mA, morepreferred values of less than 2 mA, and even more preferred values ofless than 1 mA. Commercially acceptable metal exposure values aretypically less than 2.0 mA on average.

Metal Exposure after Drop Damage

Drop damage resistance measures the ability of the coated container toresist cracks after being in conditions simulating dropping of a filledcan. The presence of cracks is measured by passing electrical currentvia an electrolyte solution, as previously described in the MetalExposure section. A coated container is filled with the electrolytesolution and the initial metal exposure is recorded. The can is thenfilled with water and dropped through a tube from a specified heightonto an inclined plane, causing a dent in the chime area. The can isthen turned 180 degrees, and the process is repeated. Water is thenremoved from the can and metal exposure is again measured as describedabove. If there is no damage, no change in current (mA) will beobserved. Typically, an average of 6 or 12 container runs is recorded.Both metal exposures results before and after the drop are reported. Thelower the milliamp value, the better the resistance of the coating todrop damage. Preferred coatings give metal exposure values after dropdamage of less than 3.5 mA, more preferred valued of less than 2.5 mA,and even more preferred values of less than 1.5 mA.

Solvent Resistance

The extent of “cure” or crosslinking of a coating is measured as aresistance to solvents, such as methyl ethyl ketone (MEK, available fromExxon, Newark, N.J.) or isopropyl alcohol (IPA). This test is performedas described in ASTM D 5402-93. The number of double-rubs (i.e., oneback-and forth motion) is reported.

Global Extractions

The global extraction test is designed to estimate the total amount ofmobile material that can potentially migrate out of a coating and intofood packed in a coated can. Typically coated substrate is subjected towater or solvent blends under a variety of conditions to simulate agiven end use. Acceptable extraction conditions and media can be foundin 21CFR 175.300 paragraphs (d) and (e). The allowable global extractionlimit as defined by the FDA regulation is 50 parts per million (ppm).

The extraction procedure used in the current invention is described in21CFR 175.300 paragraph (e) (4) (xv) with the following modifications toensure worst-case scenario performance: 1) the alcohol content wasincreased to 10% by weight and 2) the filled containers were held for a10-day equilibrium period at 100° F. These conditions are per the FDApublication “Guidelines for Industry” for preparation of Food ContactNotifications. The coated beverage can was filled with 10 weight percentaqueous ethanol and subjected to pasteurization conditions (150° F.) for2 hours, followed by a 10-day equilibrium period at 100° F.Determination of the amount of extractives was determined as describedin 21CFR 175.300 paragraph (e) (5), and ppm values were calculated basedon surface area of the can (no end) of 44 square inches with a volume of355 ml. Preferred coatings give global extraction results of less than50 ppm, more preferred results of less than 10 ppm, even more preferredresults of less than 1 ppm. Most preferably, the global extractionresults are optimally non-detectable.

Adhesion

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359—Test Method B, using SCOTCH 610 tape, available from 3M Companyof Saint Paul, Minn. Adhesion is generally rated on a scale of 0-10where a rating of “10” indicates no adhesion failure, a rating of “9”indicates 90% of the coating remains adhered, a rating of “8” indicates80% of the coating remains adhered, and so on. Adhesion ratings of 10are typically desired for commercially viable coatings.

Blush Resistance

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount of waterabsorbed into a coated film. When the film absorbs water, it generallybecomes cloudy or looks white. Blush is generally measured visuallyusing a scale of 0-10 where a rating of “10” indicates no blush and arating of “0” indicates complete whitening of the film. Blush ratings ofat least 7 are typically desired for commercially viable coatings andoptimally 9 or above.

Process or Retort Resistance

This is a measure of the coating integrity of the coated substrate afterexposure to heat and pressure with a liquid such as water. Retortperformance is not necessarily required for all food and beveragecoatings, but is desirable for some product types that are packed underretort conditions. The procedure is similar to the Sterilization orPasteurization test. Testing is accomplished by subjecting the substrateto heat ranging from 105-130° C. and pressure ranging from 0.7 to 1.05kg/cm² for a period of 15 to 90 minutes. For the present evaluation, thecoated substrate was immersed in deionized water and subjected to heatof 121° C. (250° F.) and pressure of 1.05 kg/cm² for a period of 90minutes. The coated substrate was then tested for adhesion and blush asdescribed above. In food or beverage applications requiring retortperformance, adhesion ratings of 10 and blush ratings of at least 7 aretypically desired for commercially viable coatings.

Crazing—Reverse Impact Resistance

The reverse impact measures the coated substrate's ability to withstandthe deformation encountered when impacted by a steel punch with ahemispherical head. For the present evaluation, coated substrate wassubjected to 12 in-lbs (1.36 N m) of force using BYK-Gardner “overall”Bend and Impact Tester and rated visually for micro-cracking ormicro-fracturing—commonly referred to as crazing. Test pieces wereimpacted on the uncoated or reverse side. A rating of 10 indicates nocraze and suggests sufficient flexibility and cure. A rating of 0indicates complete failure. Commercially viable coatings preferably showslight or no crazing on a reverse impact test.

Impact on Dome

Dome impact was evaluated by subjecting the dome apex of a 12 oz.beverage can to a reverse impact as described in the previous section.Craze was evaluated after impact. A rating of 10 indicates no craze andsuggests sufficient flexibility and cure. A rating of 0 indicatescomplete failure. Coatings for beverage can interiors preferably show nocraze (rating of 10) on a dome impact.

Joy Detergent Test

A 1% solution of JOY Detergent (available from Procter & Gamble) indeionized water is prepared and heated to 82° C. (180° F.). Coatedpanels are immersed in the heated solution for 10 minutes and thenremoved, rinsed, and dried. Samples are then evaluated for adhesion andblush, as previously described. Commercially viable beverage interiorcoatings preferably give adhesion ratings of 10 and blush ratings of atleast 7, optimally at least 9, in the detergent test.

Feathering

Feathering is a term used to describe the adhesion loss of a coating onthe tab of a beverage can end. When a beverage can is opened, a portionof free film may be present across the opening of the can if the coatingloses adhesion on the tab. This is feathering.

To test feathering, a “tab” is scored on the backside of a coated panel,with the coated side of the panel facing downward. The test piece isthen pasteurized as described under the Pasteurization section below.

After pasteurization, pliers are used to bend the cut “tab” to a90-degree angle away from the coated side of the substrate. The testpiece is then placed on a flat surface, coated side down. The cut “tab”is gripped using pliers and the “tab” is pulled from the test panel atan angle of 180 degrees until it is completely removed. After removingthe “tab,” any coating that extends into the opening on the test panelis measured. The distance of the greatest penetration (feathering) isreported in inches. Coatings for beverage ends preferably showfeathering below 0.2 inch (0.508 cm), more preferably below 0.1 inch(0.254 cm), most preferably below 0.05 inch (0.127 cm), and optimallybelow 0.02 inch (0.051 cm).

Dowfax Detergent Test

The “Dowfax” test is designed to measure the resistance of a coating toa boiling detergent solution. This is a general test run for beverageend coatings and is mainly used to evaluate adhesion. Historically, thistest was used to indicate problems with the interaction of coating tosubstrate pretreatment. The solution is prepared by mixing 5 ml ofDowfax 2A1 (product of Dow Chemical) into 3000 ml of deionized water.Typically, coated substrate strips are immersed into the boiling Dowfaxsolution for 15 minutes. The strips are then rinsed and cooled indeionized water, dried, and then tested and rated for blush and adhesionas described previously. Preferred beverage end coatings provideadhesion ratings of 10 and blush ratings of at least 4, more preferably6 or above in the Dowfax detergent test.

Sterilization or Pasteurization

The sterilization or pasteurization test determines how a coatingwithstands the processing conditions for different types of foodproducts packaged in a container. Typically, a coated substrate isimmersed in a water bath and heated for 5-60 minutes at temperaturesranging from 65° C. to 100° C. For the present evaluation, the coatedsubstrate was immersed in a deionized water bath for 45 minutes at 85°C. The coated substrate was then removed from the water bath and testedfor coating adhesion and blush as described above. Commercially viablecoatings preferably provide adequate pasteurization resistance withperfect adhesion (rating of 10) and blush ratings of at least 5,optimally at least 9.

Coefficient of Friction

Coefficient of friction (COF) is a measurement of lubricity of a coatingand is used to give an indication of how a cured coating will perform oncommercial fabrication equipment and presses. Typically, lubricants areadded to coatings requiring aggressive post application fabrication togive the appropriate lubricity.

For the present evaluation, an Altek Mobility/Lubricity Tester Model9505AE with a chart recorder was used to measure the COF of curedbeverage end coatings on aluminum substrates. The instrument works bypulling a sled with steel balls attached to a loadbar across the surfaceof the coated substrate, and the COF is charted out as resistance on0-10 scale chart paper. Each unit equals 0.25 COF units. Coatings of thepresent invention are formulated to give a preferred COF range of 0.055to 0.095.

Fabrication or End Continuity

This test measures the ability of a coated substrate to retain itsintegrity as it undergoes the formation process necessary to produce abeverage can end. It is a measure of the presence or absence of cracksor fractures in the formed end. The end is typically placed on a cupfilled with an electrolyte solution. The cup is inverted to expose thesurface of the end to the electrolyte solution. The amount of electricalcurrent that passes through the end is then measured. If the coatingremains intact (no cracks or fractures) after fabrication, minimalcurrent will pass through the end.

For the present evaluation, fully converted 202 standard openingbeverage ends were exposed for a period of 4 seconds to aroom-temperature electrolyte solution comprised of 1% NaCl by weight indeionized water. The coating to be evaluated was present on the interiorsurface of the beverage end at a dry film thickness of 6 to 7.5milligrams per square inch (“msi”) (or 9.3 to 11.6 grams per squaremeter), with 7 msi being the target thickness. Metal exposure wasmeasured using a WACO Enamel Rater II, available from theWilkens-Anderson Company, Chicago, Ill., with an output voltage of 6.3volts. The measured electrical current, in milliamps, is reported. Endcontinuities are typically tested initially and then after the ends aresubjected to pasteurization or retort.

Preferred coatings of the present invention initially pass less than 10milliamps (mA) when tested as described above, more preferably less than5 mA, most preferably less than 2 mA, and optimally less than 1 mA.After pasteurization or retort, preferred coatings give continuities ofless than 20 mA, more preferably less than 10 mA, even more preferablyless than 5 mA, and even more preferably less than 2 mA.

The following table lists some of the raw materials and ingredients usedin the following examples. Alternative materials or suppliers may besubstituted as is appreciated to one skilled in the art.

Chemical Name Trade Name Supplier Location Glacial Methacrylic Acid Rohm& Haas Philadelphia, PA Butyl Acrylate Rohm & Haas Philadelphia, PAStyrene Rohm & Haas Philadelphia, PA Benzoyl Peroxide Norac CompanyHelena, AR Butanol Dow Midland, MI Ethylene Glycol Butyl ether ButylCellosolve/ Dow Midland, MI Dowanol EB Butyl Methacrylate Rohm & HaasPhiladelphia, PA t-Butyl peroctoate Arkema Philadelphia, PA Ethylacrylate Rohm & Haas Philadelphia, PA Acrylic Acid Rohm & HaasPhiladelphia, PA Hydroxypropylmethacrylate ROCRYL 410 Rohm & HaasPhiladelphia, PA Hydroxyethyl methacrylate ROCRYL 400 Rohm & HaasPhiladelphia, PA Dimethylethanol amine Huntsman Dallas, TX ChemicalGlycidyl methacrylate SR 379 Sartomer, Inc Warrington, PA Hydrogenperoxide Ashland Pittsburgh, PA Chemical Benzoin Estron Calvert City, KYN--isobutoxymethyl CYLINK IBMA Cytec Ind. West Patterson, NJ acrylamidemonomer Amyl alcohol Dow Midland, MI Propylene glycol n-butyl DOWANOLPNB Dow Midland, MI ether Secondary alcohol TERGITOL 15-S-7 Dow Midland,MI ethoxylate sec-butanol Dow Midland, MI Polyethylene wax Slipayd 404Elementis Staines, UK Thermoset Phenol Based SD-912B ValsparMinneapolis, MN Phenolic Carnauba wax emulsion Michemlube 160 MichelmanCincinnati, OH PFE Isooctyl alcohol Aldrich Chemical Milwaukee, WIPolyethylene wax Lanco Glidd 5118 Lubrizol Wickliffe, OH Dipropyleneglycol Aldrich Chemical Milwaukee, WI Isophthalic acid BP Amoco Chicago,IL Dibutyl tin oxide Fastcat 4201 Arkema Philadelphia, PA Xylene ExxonNewark, NJ Trimellitic anhydride BP Amoco Chicago, IL Iron ComplexHamp-OL Traylor Chemical Orlando, FL 4.5% Iron Erythorbic acid AldrichChemical Milwaukee, WI t-butyl hydroperoxide Trigonox A-W70 AkzoPhiladelphia, PA Ethylene glycol Ashland Pittsburgh, PA Chemical Sebacicacid Ivanhoe Tampa. FL Industries 1,4-cyclohexane dimethanol CHDM-90Eastman Kingsport, TN 90% in water Butyl Stannoic acid Fastcat 4100Arkema Philadelphia, PA 4-Hydroxybenzoic acid Acros Organics Houston, TXthrough Fisher Scientific 1,4-Cyclohexane Erisys GE-22 CVC SpecialtyMaple Shade, NJ dimethanol diglycidyl ether Chemicals EthyltriphenylCatalyst 1201 Deepwater Woodward, OK phosphonium iodide ChemicalsSuccinic ahydride JLM Marketing Tampa, FL Bisphenol A Dow Midland, MIBispenol A diglycidyl ether Epon 828 Resolution Houston, TX PerformanceProducts Methylisobutyl ketone Dow Midland, MI Dibasic ester DupontWilmington, DE Propylene glycol methyl Dowanol PM Dow Midland, MI ether

Example 1 Run 1—Preparation of Acid-Functional Acrylic

A premix of 512.6 parts glacial methacrylic acid (MAA), 512.6 partsbutyl acrylate (BA), 114.0 parts styrene, and 73.2 parts benzoylperoxide (70% water wet) was prepared in a separate vessel. A 3-literflask was equipped with a stirrer, reflux condenser, thermocouple,heating mantle, and nitrogen blanket. Ten percent of the premix wasadded to the flask along with 405.9 parts butanol and 30.6 partsdeionized water. To the remaining premix were added 496.1 parts butanoland 38.3 parts deionized water. With the nitrogen blanket flowing in theflask, the contents were heated to 93° C. At 93° C., external heatingwas stopped and the material was allowed to increase in temperature for15 minutes. After 15 minutes, the batch was at 97° C., and the remainingpremix was added uniformly over 2 hours maintaining 97° C. to 100° C.When the premix addition was complete, the premix vessel was rinsed with5 parts butanol. The batch was held at temperature for 2.5 hours. Theheating was discontinued and 317.7 parts butyl cellosolve was added. Theresulting acrylic prepolymer was 44.3% solids (NV), with an acid numberof 313 and a Brookfield viscosity (as determined by ASTM D-2196) of4,990 centipoise (cps).

Example 1 Run 2—Preparation of Acid-Functional Acrylic

A premix of 677.7 parts glacial methacrylic acid, 677.7 parts butylmethacrylate (BMA), 150.8 parts styrene, and 96.9 parts benzoyl peroxide(70% water wet) was prepared in a separate vessel. A 5-liter flask wasequipped with a stirrer, reflux condenser, thermocouple, heating mantle,and nitrogen blanket. Ten percent of the premix was added to the flaskalong with 536.9 parts butanol and 40.7 parts deionized water. To theremaining premix were added 758.1 parts butanol and 50.6 parts deionizedwater. With the nitrogen blanket flowing in the flask, the contents wereheated to 93° C. At 93° C., external heating was stopped, and thematerial was allowed to increase in temperature for 10 minutes. After 10minutes, the batch was at 98° C., and the remaining premix was addeduniformly over 2 hours maintaining 97° C. to 100° C. The batch was heldat temperature for 3 hours. The heating was discontinued and the batchcooled. The resulting acrylic prepolymer was 49.9% NV, with an acidnumber of 304 and a Brookfield viscosity of 101,000 cps.

Example 1 Run 3—Preparation of Acid-Functional Acrylic

A premix of 802.6 parts glacial methacrylic acid, 807 parts butylmethacrylate, 178.5 parts styrene, 80.3 parts t-butyl peroctoate, 838.5parts butanol, and 59.9 parts deionized water was prepared in a separatevessel. A 5-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Added to the 5 literflask were 635.8 parts butanol and 48.1 parts deionized water. The flaskwas heated to 94° C. At 94° C., 12.5 parts t-butyl peroctoate wereadded. The batch was held for 5 minutes after which the premix was addedover 2.5 hours. A second premix containing 59.2 parts butanol and 16.1parts t-butyl peroctoate was prepared. When the addition of the firstpremix was complete the second premix was added over 30 minutes. Oncecomplete, the batch was held for 30 minutes. A chase of 3.4 partst-butyl peroctoate was added and the batch held for 2 hours. After the2-hour hold time, the heat was discontinued and the batch cooled. Theresulting acrylic prepolymer was 50.1% NV, with an acid number of 292and a Brookfield viscosity of 150,000 cps.

Example 1 Run 4—Preparation of Acid-Functional Acrylic

A premix of 802.6 parts glacial methacrylic acid, 445.9 parts ethylacrylate, 535.1 parts styrene, 108.6 parts t-butyl peroctoate, 838.5parts butanol, and 59.9 parts deionized water was prepared in a separatevessel. A 5-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Added to the 5-literflask was 635.8 parts butanol and 48.1 parts deionized water. The flaskwas heated to 94° C. At 94° C., 16.6 parts t-butyl peroctoate was added.The batch was held for 5 minutes after which the premix was added over2.5 hours. A second premix containing 59.2 parts butanol and 21.2 partst-butyl peroctoate was prepared. When the addition of the first premixwas complete, the second premix was added over 30 minutes. Oncecomplete, the batch was held for 30 minutes. A chase of 4.6 partst-butyl peroctoate was added and the batch held for 2 hours. After the2-hour hold, the heat was discontinued and the batch cooled. Theresulting acrylic prepolymer was 49.8% NV, with an acid number of 303and a Brookfield viscosity of 21,650 cps.

Example 1 Runs 5-11

Using techniques from Example 1: Run 4, the systems shown in Table 1were prepared.

TABLE 1 Acid-Functional Acrylics Ex. 1: Run 4 Run 5 Run 6 Run 7 Run 8Run 9 Run 10 Run 11 MAA 45 30 45 0 30 45 25 45 EA 25 50 45 23 0 15 30 0Styrene 30 5 10 10 25 0 25 10 BMA 0 15 0 31 0 40 0 45 AA¹ 0 0 0 36 0 0 00 BA 0 0 0 0 45 0 0 0 HPMA² 0 0 0 0 0 0 20 0 Solids 49.8% 62.8% 49.4%51.4% 55.4% 49.6% 50.5% 49.7% Acid No. 303 198 295 246 192 293 155 292Brookfield 21,650 50,000 8,730 1,100 6,660 27,800 3,532 106,000 Visc.(cps) ¹Glacial acrylic acid ²Hydroxypropyl methacrylate

Example 1 Run 12—Preparation of Acid-Functional Acrylic

A premix of 803.4 parts glacial methacrylic acid, 446.3 parts ethylacrylate (EA), 535.5 parts styrene, 153 parts benzoyl peroxide (70%water wet), 839.2 parts butanol, and 60 parts deionized water wasprepared in a separate vessel. A 5-liter flask was equipped with astirrer, reflux condenser, thermocouple, heating mantle and nitrogenblanket. To the flask, 636.3 parts butanol and 48.2 parts deionizedwater were added and heated to 97° C. to 100° C. with a nitrogen blanketflowing in the flask. The premix was added uniformly over 2.5 hoursmaintaining 97° C. to 100° C. When the premix was in, the premix vesselwas rinsed with 59.2 parts butanol and added to the flask. The batch washeld at temperature for 2 hours. The heating was discontinued and thebatch cooled. The resulting acrylic prepolymer was 50.2% NV, with anacid number of 301 and a Brookfield viscosity of 25,400 cps.

Example 1 Runs 13-15

Using techniques from Example 1: Run 12 the systems shown in Table 2were prepared.

TABLE 2 Acid-Functional Acrylics Example No. 1: Run 12 Run 13 Run 14 Run15 MAA 45 25 35 25 EA 25 25 25 33 Styrene 30 30 30 22 HPMA 0 20 10 20Solids 51.2% 50.2% 50.0% 50.3% Acid Number 301 171 234 169 Brookfield25,400 2,820 6,020 2,220 Viscosity (cps)

Example 2 Run 1—Preparation of Salt of Acid-Functional Acrylic

A 3-liter flask was equipped with a stirrer, reflux condenser, DeanStark Tube, thermocouple, heating mantle, and nitrogen blanket. Into theflask was added 711.5 parts of Example 1: Run 1 acrylic, 762.9 partsdeionized water, and 56.9 parts dimethyl ethanol amine (DMEA). Thecontents were heated to reflux and 553 parts were distilled from theflask. After distillation was complete, 598 parts of deionized waterwere added. The batch was cooled giving an acrylic solution at 20.3%solids and 307 acid number.

Example 2 Run 2—Preparation of Salt of Acid-Functional Acrylic

A 5-liter flask was equipped with a stirrer, reflux condenser, DeanStark Tube, thermocouple, heating mantle, and nitrogen blanket. Into theflask was added 1853 parts of Example 1: Run 2 acrylic, 2220.4 partsdeionized water, and 163.3 parts dimethyl ethanol amine. The contentswere heated to reflux and 1587 parts were distilled from the flask.After distillation was complete, 1718 parts of deionized water wereadded. The batch was cooled giving an acrylic solution at 22.2% solids,294 acid number, pH of 6.0, and a viscosity of 13 seconds (Number 4 Fordcup viscosity as determined by ASTM D-1200).

Example 2 Run 3—Preparation of Salt of Acid-Functional Acrylic

A 5-liter flask was equipped with a stirrer, reflux condenser, DeanStark Tube, thermocouple, heating mantle, and nitrogen blanket. Into theflask was added 1852.3 parts of Example 1: Run 3 acrylic, 2219 partsdeionized water, and 163 parts dimethyl ethanol amine The contents wereheated to reflux and 1463 parts were distilled from the flask. Afterdistillation was complete, 1581 parts of deionized water were added. Thebatch was cooled giving an acrylic solution at 21.6% solids, 284 acidnumber, pH of 6.23 and a viscosity of 13 seconds (Number 4 Ford cup).

Example 2 Run 4—Preparation of Salt of Acid Functional Acrylic

A 5-liter flask was equipped with a stirrer, reflux condenser, DeanStark Tube, thermocouple, heating mantle, and nitrogen blanket. Into theflask was added 1799.2 parts of Example 1: Run 4 acrylic, 2155.9 partsdeionized water, and 158.6 parts dimethyl ethanol amine The contentswere heated to reflux and 1541 parts were distilled from the flask.After distillation was complete, 1615 parts of deionized water wereadded. The batch was cooled giving an acrylic solution at 22.1% solids,302 acid number, pH of 6.55 and a Brookfield viscosity of 2060 cps.

Example 2 Runs 5-15

Using techniques from Example 2: Run 4 the systems shown in Table 3 wereprepared. Each run of Example 2 used the correspondingly numbered runfrom Example 1. That is, Example 2: Run 5 used the acrylic prepolymerfrom Example 1: Run 5, etc.

TABLE 3 Acid-Functional Acrylic Salts Ex 2: Run 4 Run 5 Run 6 Run 7 Run8 Run 9 Solids 22.1% 21.4% 21.6% 22.0% 21.7% 21.3% Acid 302 198 291 248193 291 No. PH 6.55 6.49 5.96 5.95 7.30 6.26 Viscos- 2,060 cps 1,050 cps1,770 cps — — 20 sec ity¹ Ex. 2: Run 10 Run 11 Run 12 Run 13 Run 14 Run15 Solids 21.7% 21.7% 22.0% 21.3% 21.7% 22.2% Acid No. 153 300 291 169231 271 pH 7.29 6.54 6.37 6.72 — 6.67 Viscosity¹ 881 cps 15 sec 167 cps304 cps 248 cps 1900 cps ¹Brookfield viscosity values in cps and Number4 Ford cup viscosity values in sec.

Example 3 Run 1—Emulsion

A 1-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wereadded 313.9 parts of Example 2: Run 3 salt and 267.3 parts deionizedwater. The contents of the flask were heated to 75° C. at 280revolutions per minute (RPM). In a separate vessel, a premix of 71.4parts styrene, 116.3 parts butyl methacrylate, and 16.3 parts glycidylmethacrylate (GMA) was prepared. Once the flask was at 75° C., 10% ofthe premix was added followed by 2.04 parts benzoin and 20 partsdeionized water. The flask was heated further to 79° C. At 79° C., 2.04parts of 35% hydrogen peroxide was added and held for 5 minutes. After 5minutes, the temperature control was set at 81° C. and the remainingpremix was added over a period of 1 hour. When the addition wascomplete, 20 parts deionized water were used to rinse the residualpremix into the flask. The batch was held for 10 minutes and then 0.35part benzoin, 20 parts deionized water, and 0.35 part 35% hydrogenperoxide were added. After 2 hours the heat was removed and the batchcooled. This gave an emulsion at 31.9% solids, 63.3 acid number, pH of6.48, and a Brookfield viscosity of 203 cps.

Example 3 Run 2—Emulsion

A 0.5-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 155.6 parts of Example 2: Run 4 salt and 120.6 parts deionizedwater. The contents of the flask were heated to 75° C. at 240 RPM. In aseparate vessel, a premix of 66.3 parts styrene, 19.6 parts ethylacrylate, and 7.5 parts glycidyl methacrylate was prepared. Once theflask was at 75° C., 10% of the premix was added followed by 0.91 partbenzoin and 9.4 parts deionized water. The flask was heated further to79° C. At 79° C., 0.91 part of 35% hydrogen peroxide was added and heldfor 5 minutes. After 5 minutes, the temperature control was set at 81°C. and the remaining premix was added over 1 hour. When the addition wascomplete, 9.4 parts deionized water were used to rinse the residualpremix into the flask. The batch was held for 10 minutes and then 0.16part benzoin, 9.4 parts deionized water, and 0.16 part 35% hydrogenperoxide were added. After 2 hours, the heat was removed and the batchcooled. This gave an emulsion at 30.9% solids, 83.8 acid number, pH of6.70, and a viscosity of 40 seconds (Number 4 Ford cup).

Example 3 Run 3—Emulsion

A 1-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 311.2 parts of Example 2: Run 4 salt and 241.2 parts deionizedwater. The contents of the flask were heated to 75° C. at 270 RPM. In aseparate vessel, a premix of 112.1 parts styrene, 59.8 parts ethylacrylate, and 14.9 parts glycidyl methacrylate was prepared. Once theflask was at 75° C., 10% of the premix was added followed by 1.87 partsbenzoin and 18.8 parts deionized water. The flask was heated further to79° C. At 79° C., 1.87 parts of 35% hydrogen peroxide were added andheld for 5 minutes. After 5 minutes, the temperature control was set at81° C. and the remaining premix was added over 1 hour. When the additionwas complete, 18.8 parts deionized water were used to rinse the residualpremix into the flask. The batch was held for 10 minutes and then 0.32part benzoin, 18.8 parts deionized water, and 0.32 part 35% hydrogenperoxide were added. After 2 hours, the heat was removed and the batchcooled. This gave an emulsion at 31.8% solids, 76.7 acid number, pH of6.67, and a viscosity of 28 seconds (Number 4 Ford cup).

Example 3 Run 4—Emulsion

A 5-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 1525.0 parts of Example 2: Run 4 salt and 1219.1 parts deionizedwater. The contents of the flask were heated to 70° C. at 250 RPM. In aseparate vessel a premix of 380.4 parts styrene, 278.3 parts butylacrylate (BA), 194.9 parts butyl methacrylate, and 74.2 parts glycidylmethacrylate was prepared. Once the flask was at 70° C., 10% of thepremix was added followed by 9.29 parts benzoin and 92.9 parts deionizedwater. The flask was heated further to 79° C. At 79° C., 9.29 parts of35% hydrogen peroxide were added and held for 5 minutes. After 5minutes, the temperature control was set at 81° C. and the remainingpremix was added over 1 hour. When the addition was complete, 92.9 partsdeionized water were used to rinse the residual premix into the flask.The batch was held for 10 minutes and then 1.59 parts benzoin, 92.9parts deionized water, and 1.59 parts 35% hydrogen peroxide were added.The batch was held for 45 minutes and then 0.52 part benzoin and 0.52part 35% hydrogen peroxide were added. After 2 hours, the heat wasremoved and the batch cooled. This gave an emulsion at 31.4% solids,64.1 acid number, pH of 6.95, and a viscosity of 22 seconds (Number 4Ford cup).

Example 3 Run 5—Emulsion

A 12-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 3886.5 parts of Example 2: Run 4 salt and 3022.5 parts deionizedwater. The contents of the flask were heated to 70° C. at 235 RPM. In aseparate vessel, a premix of 771.25 parts styrene, 933.75 parts butylacrylate, 537.5 parts butyl methacrylate, and 93.75 parts glycidylmethacrylate was prepared. Once the flask was at 70° C., 23.38 partsbenzoin and 116.25 parts deionized water followed by 10% of the premixwere added. The flask was heated further to 79° C. At 79 ° C., 23.38parts of 35% hydrogen peroxide and 116.25 parts deionized water wereadded and held for 5 minutes. After 5 minutes, the temperature controlwas set at 81° C. and the remaining premix was added over 1 hour. Whenthe addition was complete, 232.5 parts deionized water were used torinse the residual premix into the flask. The batch was held for 10minutes and then 4.0 parts benzoin, 232.5 parts deionized water, and 4.0parts 35% hydrogen peroxide were added. The batch was held for 45minutes and then 1.25 parts benzoin and 1.25 parts 35% hydrogen peroxidewere added. After 2 hours, the heat was removed and the batch cooled.This gave an emulsion at 31.4% solids, 72.4 acid number, pH of 7.05, anda viscosity of 32 seconds (Number 4 Ford cup).

Example 3 Runs 6-10

Using the process outlined in Example 3: Run 4 the Emulsions shown inTable 4 were prepared.

TABLE 4 Emulsions Example 3: Run 4 Run 6 Run 7 Run 8 Run 9 Run 10Acrylic salt Ex. 2: Run 4 Ex. 2: Run 4 Ex. 2: Run 4 Ex. 2: Ex. 2: Run 4Ex. 2: Run 4 Run 4 Monomers Styrene 41.0 39.0 42.0 43.5 43.5 45.0 BA30.0 53.0 54.0 54.5 54.5 55.0 BMA 21.0 0.0 0.0 0.0 0.0 0.0 GMA 8.0 8.04.0 2.0 2.0 0.0 Emulsion Good Good Good White- White-Low EmulsionComments Appearance Appearance Appearance High Conversion SeparatedViscosity Solids 31.4% 31.3% 31.5% 31.7% 28.6% 31.2% Viscosity 22 sec 51sec 103 sec — 22 sec — (No. 4 Ford Cup) Brookfield — 230 cps 610 cps25,000 cps — — Viscosity pH 6.95 7.05 6.88 — 6.65 —

This resin series showed that as the GMA level decreased, acceptableemulsions became more difficult to produce.

Example 3 Runs 11-18

A design experiment using Example 2: Run 9 as the acid functionalacrylic salt and the process outlined above was prepared and is depictedin Table 5.

TABLE 5 Emulsion Design Experiment Example 3: Run 11 Run 12 Run 13 Run14 Run 15 Run 16 Run 17 Run 18 Acrylic/Monomer Ratio 73/27 65/35 MonomerMonomer Monomer Monomer Composition 1 Composition 2 Composition 1Composition 2 GMA Level Low High Low High Low High Low High MonomersStyrene 42 39 33 33 43 41 33 33 BA 54 53 40 41 54 53 40 40 BMA 0 0 23 180 0 24 21 GMA 4 8 4 8 3 6 3 6 Solids 32.0% 31.3% 31.6% 31.9% 31.6% 32.0%31.7% 32.0% Viscosity — 63 sec — — 35 sec 210 sec 42 sec — (No. 4 FordCup) Brookfield 10,000 — 10,000 695 — — — 1,384 Viscosity (cps) AcidNumber 74.7 72.9 74.9 70.2 101 96.1 101 96.5

The latices from Table 5 were tested without further modification orformulation, and the results are shown in Table 6. Each composition wasdrawn down onto Alcoa ALX aluminum at a film weight of 7-8 milligramsper square inch (msi) (1.1-1.25 milligrams per square centimeter(mg/cm²)) and cured for 10 seconds to achieve a 420° F. (215° C.) peakmetal temperature in a gas fired coil oven.

TABLE 6 Beverage End Film Performance Waterbased Ex. 3: Ex. 3: Ex. 3:Ex. 3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Control¹ Run 11 Run 12 Run 13 Run 14Run 15 Run 16 Run 17 Run 18 Craze None None None None None None SlightNone None MEK Resistance 19 5 6 3 7 5 6 4 8 Feathering⁴ 0.343 0.0130.020 0.071 0.003 0.020 0.013 0.030 0.013 Water Retort² Blush 9.5 10 9.59.5 9.5 9 10 8 10 Adhesion 10 10 10 10 10 10 10 10 10 Pasteurization³Blush 10 10 10 10 10 10 10 10 10 Adhesion 10 10 10 10 10 10 10 10 10 EndContinuity Initial 0 0.22 25.3 11.5 57.8 17.7 133.5 27.5 132.2 AfterRetort² 8.4 31.8 Not Tested 31.7 Not Tested Not Tested Not Tested 34.3Not Tested ¹Commercially available beverage end coating from Valsparcoded 13Q80AG. ²90 minutes at 121° C. (250° F.). ³30 minutes at 85° C.(185° F.). ⁴Performed after a 45 minutes at 85° C. (185° F.)pasteurization. Measured in centimeters.

Example 3 Runs 5b and 19-25

A design experiment using Example 2: Run 4 as the acid functionalacrylic salt and the process outlined above was prepared and is depictedin Table 7. Example 3: Run 5b was included as one of the variables andwas a repeat of Run 5.

TABLE 7 Emulsion Design Experiment Example 3: Run 19 Run 20 Run 5b Run21 Run 22 Run 23 Run 24 Run 25 Acrylic/Monomer Ratio 73/27 65/35 MonomerMonomer Monomer Monomer Composition 1 Composition 2 Composition 1Composition 2 GMA Level Low High Low High Low High Low High MonomersStyrene 42 39 33 33 43 41 33 33 BA 54 53 40 41 54 53 40 40 BMA 0 0 23 180 0 24 21 GMA 4 8 4 8 3 6 3 6 Solids 31.5% 31.6% 31.6% 31.4% 31.3% 31.6%31.5% 31.7% Viscosity 55 sec 60 sec 50 sec 56 sec 106 sec — 70 sec —(No. 4 Ford Cup) Brookfield — — — — — 2,624 — 3,000 Viscosity (cps) AcidNumber 71.9 73.0 69.0 68.3 95.4 92.5 94.7 98.0

The lattices from Table 7 were tested without further modification orformulation, and the results are shown in Table 8. Each composition wasdrawn down onto Alcoa ALX aluminum at a film weight of 7-8 msi (1.1-1.25mg/cm²) and cured for 10 seconds to achieve a 420° F. (215° C.) peakmetal temperature in a gas fired coil oven.

TABLE 8 Beverage End Film Performance Waterbased Ex. 3: Ex. 3: Ex. 3:Ex. 3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Control¹ Run 19 Run 20 Run 5b Run 21Run 22 Run 23 Run 24 Run 25 Craze None None None None None None SlightNone Yes MEK 19 4 7 4 10 6 11 4 6 Feathering⁴ 0.343 0.064 0.051 0.0380.033 0.056 0.013 0.046 0.013 Water Retort² Blush 9.5 9.5 9.5 10 10 9.510 7 9.5 Adhesion 10 10 10 10 10 10 10 10 10 Pasteurization³ Blush 10 1010 10 10 10 10 10 10 Adhesion 10 10 10 10 10 10 10 10 10 End ContinuityInitial 0 5.5 2.6 6.0 12.3 20.2 61.2 1.9 93.6 After Retort² 8.4 23.5 14323.4 134.0 78.8 Not Tested 52.5 Not Tested ¹Commercially availablebeverage end coating from Valspar coded 13Q80AG. ²90 minutes at 121° C.(250° F.). ³30 minutes at 85° C. (185° F.). ⁴Performed after a 45minutes at 85° C. (185° F.) pasteurization. Measured in centimeters.

Example 3 Runs 26-33

A design experiment using Example 2: Run 11 as the acid functionalacrylic salt and the process outlined above was prepared and is depictedin Table 9.

TABLE 9 Emulsion Design Experiment Example 3: Run 26 Run 27 Run 28 Run29 Run 30 Run 31 Run 32 Run 33 Acrylic/Monomer Ratio 73/27 65/35 MonomerMonomer Monomer Monomer Composition 1 Composition 2 Composition 1Composition 2 GMA Level Low High Low High Low High Low High MonomersStyrene 42 39 33 33 43 41 33 33 BA 54 53 40 41 54 53 40 40 BMA 0 0 23 180 0 24 21 GMA 4 8 4 8 3 6 3 6 Solids 31.0% 31.8% 31.5% 31.4% 30.9% 31.3%31.4% 31.6% Viscosity 40 sec 48 sec — 17 sec 14 sec 16 sec 14 sec 16 sec(No. 4 Ford Cup) Brookfield — — 17,000 — — — — — Viscosity (cps) AcidNumber 73.5 68.7 71.2 68.6 97.0 93.9 99.3 93.9

The latices from Table 9 were tested without further modification orformulation, and the results are shown in Table 10. Each composition wasdrawn down onto Alcoa ALX aluminum at a film weight of 7-8 msi (1.1-1.25mg/cm²) and cured for 10 seconds to achieve a 420° F. (215° C.) peakmetal temperature in a gas fired coil oven.

TABLE 10 Beverage End Film Performance of Emulsion DOE C Waterbased Ex.3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Ex. 3: Control¹ Run 26 Run27 Run 28 Run 29 Run 30 Run 31 Run 32 Run 33 Craze None Slight None NoneYes Yes Yes Yes Yes MEK 19 7 8 3 12 3 5 7 6 Feathering⁴ 0.343 0.0460.043 0.013 0.025 0.013 0.013 0.020 0.013 Water Retort² Blush 9.5 9.510.0 9.5 10 2 10 3 9.5 Adhesion 10 10 10 10 10 10 10 10 10Pasteurization³ Blush 10 10 10 10 10 10 10 10 10 Adhesion 10 10 10 10 1010 10 10 10 End Continuity Initial 0 82.4 107.4 12.2 215.6 178.9 315.9161.5 336.9 After Retort² 8.4 Not Tested Not Tested Not Tested NotTested Not Tested Not Not Not Tested Tested Tested ¹Commerciallyavailable beverage end coating from Valspar coded 13Q80AG. ²90 minutesat 121° C. (250° F.). ³30 minutes at 85° C. (185° F.). ⁴Performed aftera 45 minutes at 85° C. (185° F.) pasteurization. Measured incentimeters.

The following are some of the conclusions drawn from results of theemulsion DOEs shown in Tables 5 through 10. The non styrene-containingacrylic stabilizer polymer from Example 2: Run 9 produced higherviscosity emulsions, which are less desirable for some end uses. Thecomposition from Example 2: Run 4 gave better overall film performance.In general, a higher acrylic polymer/monomer ratio tended to give poorerfilm integrity (continuities). Higher GMA levels in the emulsion monomermix tended to give higher emulsion viscosities and greater increases infilm continuity mAs after retort. Little difference was noticed betweenthe various co-monomer compositions, so there is latitude to vary theoverall emulsion monomer composition.

Example 3 Runs 34-35

A series of emulsions, shown in Table 11 were prepared using a monomerto acid-functional acrylic ratio of 73/27 solids/solids. These systemswere prepared using the process outlined in Example 3: Run 5 usingExample 2: Run 4 as the acid-functional acrylic salt.

TABLE 11 Emulsion GMA Level Study Example 3: Run 5b Run 34 Run 35 GMALevel   4%   12%   20% Monomers Styrene 33 33 33 BA 40 42 44 BMA 23 13 3GMA 4 12 20 Solids 31.6% 31.8% 32.0% Viscosity (No. 4 Ford cup) 50 sec —— Brookfield Visc. (cps) — 1,070 33,950 Acid Number 69.0 59.5 44.9

It can be seen that as the GMA level was increased, the resulting acidnumber decreased, indicating the GMA consumed some of the acid groups onthe acrylic polymer stabilizer.

Example 3 Runs 36-42

A series of emulsions, shown in Table 12, were prepared using a monomerto acid-functional acrylic ratio of 73/27 solids/solids. These systemswere prepared using the process outlined in Example 3: Run 5b usingExample 2: Run 10 as the acid-functional acrylic salt. This acryliccontains hydroxyl functionality that may theoretically co-react with theIBMA during cure.

TABLE 12 Effect of IBMA in Emulsions Example 3: Run 36 Run 37 Run 38 Run39 Run 40 Run 41 Run 42 IBMA Level   0%   4%   5%   6%   7%   8%   12%Monomers Styrene 33 26 26 26 26 26 26 BA 40 45 46 46 46 47 48 BMA 23 2119 18 17 15 10 GMA 4 4 4 4 4 4 4 IBMA¹ 0 4 5 6 7 8 12 Solids % 31.4%31.6% 30.9% 30.4% 30.4% 30.0% 29.8% Viscosity 22 sec 17 sec 18 sec 16sec 16 sec 16 sec 17 sec (No. 4 Ford Cup) Acid Number 38.1 40.1 40.939.5 40.5 41.0 40.4 ¹N-Isobutoxymethyl acrylamide

The latices from Table 12 were tested without further modification orformulation, and the results are shown in Table 13. Each composition wasdrawn down onto Alcoa ALX aluminum at a film weight of 7-8 msi (1.1-1.25mg/cm²) and cured for 10 seconds to achieve a 420° F. (215° C.) peakmetal temperature in a gas fired coil oven.

TABLE 13 Beverage End Continuities (IBMA Level) Example 3: Run Run RunRun Run 36 Run 37 Run 38 39 40 41 42 IBMA Level 0% 4% 5% 6% 7% 8% 12%End Continuity Initial 3 1.5 1.1 1.0 0.4 0.9 0.7 After Retort¹ 19 12 4.36.5 6.6 9.3 31 ¹90 minutes at 250° F. (121° C.).

Results from Table 13 indicate the optimum level of IBMA in the emulsionmonomer composition is around 5%, when used in conjunction with hydroxylfunctionality in the acrylic polymer stabilizer.

Example 4 Runs 1-2—Spray Application

The water-based emulsion of Example 3: Run 4 was successfully formulatedinto a spray applied coating for the interior of beer/beverage aluminumcans. The product was formulated with or without additional surfactant,as described in Table 14.

TABLE 14 Beverage Inside Spray Coating Compositions Example 4:Composition (parts) Run 1 Run 2 Example 3: Run 4 62 65 Butanol 6 5 ButylCellosolve 3 0 Amyl Alcohol 1 0 Dowanol PNB¹ 0 5 TERGITOL 15-S-7² 0 1Deionized Water 28 24 Formulation Solids, % 20 21 Viscosity, No. 4 Fordcup 20 sec 30 sec VOC, kg/l - H₂O 0.358 0.358 ¹Commercially availablefrom Dow Chemical. ²Commercially available surfactant from Dow Chemical.

These formulations were sprayed at typical laboratory conditions at 120milligram per can (mg/can) to 130 mg/can coating weight for theapplication of interior beverage coatings, and cured at 188° C. to 199°C. (measured at the can dome) for 30 seconds through a gas oven conveyorat typical heat schedules for this application. The film propertiesshown in Table 15 were achieved.

TABLE 15 Inside Spray Film Properties Example 4: Run 1 Run 2 MetalExposures Initial 2 mA 3 mA After drop damage 2 mA 7 mA MEK resistance<2 <2 Water retort¹ Blush None None Adhesion Excellent Excellent Globalextraction² 0.25 ppm 3.8 ppm ¹90 minutes at 250° F. (121° C.). ²2 hoursat 150° F. in 90% aqueous ethanol.

The cured films displayed excellent resistance properties and low globalextractions despite the fact that their solvent resistance as determinedby MEK rubs is low. The higher global extraction result for Example 4:Run 2 was determined to be due to the surfactant present.

Example 4 Runs 3-4—Spray Application

The water-based emulsion of Example 3: Run 4 and Example 3: Run 7 weresuccessfully formulated into spray applied coatings for the interior ofbeer/beverage aluminum cans. Coating compositions are shown in Table 16.

TABLE 16 Inside Spray Coating Compositions Example 4: Composition(Parts) Run 3 Run 4 Example 3 Run 4 62.8 0 Example 3 Run 7 0 62.8Deionized water 22.1 22.1 Butanol 5.9 5.3 Butyl Cellosolve 2.9 2.9 Amylalcohol 1.3 1.3 Secondary butanol 0 0.5 Deionized water 5.0 5.1 Dimethylethanolamine As Needed As Needed Formulation solids 20.7% 20.4%Viscosity (No. 4 Ford cup) 20 sec 16 sec

These formulations were sprayed at typical laboratory conditions at 120mg/can to 130 mg/can (12-ounce) coating weight for the application ofinterior beverage coatings, and cured at 188° C. to 199° C. (measured atthe can dome) for 30 seconds through a gas oven conveyor at typical heatschedules for this application. The film properties shown in Table 17were achieved, using a commercial epoxy-acrylate coating as a control.

TABLE 17 Inside Spray Film Properties Waterbased Example 4: Example 4:Control¹ Run 3 Run 4 Coating weight, mg/can 124 123 121 Metal ExposuresInitial 0.9 mA 2.2 mA 0.5 mA After drop damage 1.3 mA 2.9 mA 1.2 mA MEKResistance 20-50 2-5 <1 Impact on Dome 10 10 10 IsopropanolResistance >100 >100 5-10 Water retort² Blush 7 10 10 Adhesion 10 10 10Joy Detergent Test Blush 7 10 10 Adhesion 10 10 10 Global extractions³<0.1 ppm⁴ <0.1 ppm⁴ <0.1 ppm⁴ ¹Commercially available inside beveragecan coating from Valspar coded 10Q45AF. ²90 minutes at 250° F. (121°C.). ³2 hours at 150° F. in 90% aqueous ethanol. ⁴Below the currentdetection limit.

As can be seen in Table 17, the coatings of the present inventioncompare favorably to the commercial epoxy-acrylate coating, and there isa substantial benefit for retort resistance.

Example 5 Run 1—Beverage End Coil Coating

In a jar with an agitator, 483.25 parts of Example 3: Run 5 emulsion wasstirred with 16.75 parts SLIPAYD 404 wax. The mixture was stirred for 10minutes to make it uniform. The mixture was then filtered. The mixturewas approximately 31% solids. The mixture was applied at 7-8 milligramsper square inch (msi) (1.1-1.25 mg/cm²) on ALX Alcoa aluminum and bakedfor 10 seconds (sec) to achieve a 400° F. (204° C.) peak metaltemperature in a coil oven. It was also applied at 7-8 msi (1.1-1.25mg/cm²) on ALX Alcoa aluminum and baked for 10 seconds to achieve a 435°F. (224° C.) peak metal temperature in a coil oven. Film properties areshown in Table 18.

TABLE 18 Beverage End Film Properties Waterbased Control¹ Example 5 Run1 Bake 10 sec to 10 sec to 10 sec to 10 sec to achieve achieve achieveachieve 400° F. 435° F. 400° F. 435° F. (204° C.) (224° C.) (204° C.)(224° C.) MEK Res. 23 35 4 4 Feathering² 0.500 0.193 0.018 0.010 Dowfax³Blush 4 9 4 9 Adhesion 10 10 10 10 Pasteurization⁴ Blush 6 9 5 10Adhesion 10 10 10 10 Water Retort⁵ Blush 6.5 10 5.5 10 Adhesion 10 10 1010 End Continuities Initial After Initial After Initial After InitialAfter Pasteurization⁴ 0.13 0.33 0.06 0.28 2.76 21.35 1.5 17.9 WaterRetort⁵ 0.016 2.22 0.06 0.52 4.16 22.9 1.4 17.55 ¹Commercially availablebeverage end coating from Valspar coded 13Q80AG. ²Performed after a 45minutes at 85° C. (185° F.) pasteurization. Measured in centimeters. ³15minutes at 100° C. (212° F.). ⁴30 minutes at 85° C. (185° F.). ⁵90minutes at 121° C. (250° F.).

Example 5 Runs 2-4—Beverage End Coatings

Using the process of Example 5: Run 1, the formulations shown in Table19 were prepared to investigate the effect of GMA level on endcontinuities. Each formula was applied at 7-8 msi (1.1-1.25 mg/cm²) onALX Alcoa aluminum and baked for 10 seconds to achieve a 420° F. (215°C.) peak metal temperature in a coil oven. End continuities are shown inTable 20.

TABLE 19 Effect of GMA Level Example 5: Run 2 Run 3 Run 4 Example 3 Run5 95.7 0 0 Example 3 Run 34 0 95.7 0 Example 3 Run 35 0 0 95.7 Phenolic¹2.3 2.3 2.3 SLIPAYD 404 1.5 1.5 1.5 Michem Lube 160 PFE² 0.5 0.5 0.5Water/Solvent³ To 23% Solids To 23% Solids — Deionized Water — — To 23%Solids ¹A phenol-formaldehyde phenolic at 50% in water, prepared byreacting 2.3 moles of formaldehyde with 1 mole of phenol. ²Commerciallyavailable lubricant from Michelman Inc. ³1:1 Blend of deionized waterand isopropyl alcohol.

TABLE 20 Effect of GMA Level on Beverage End Performance Example 5: Run2 Run 3 Run 4 GMA Level 4% 12% 20% End Continuities Initial  2  49 149After Retort¹ 21 193 304 ¹90 minutes at 121° C. (250° F.).

As can be seen by the data in Table 20, lower GMA levels appear toprovide better film integrity on fabricated ends, especially after aretort.

Example 5 Run 5—Beverage End Coating

Using the process of Example 5: Run 1, the formulation shown in Table 21was prepared. The formula was applied at 7-8 milligrams per square inch(msi) (1.1-1.25 mg/cm²) on ALX Alcoa aluminum and baked for 10 secondsto achieve 400° F. (204° C.) and 420° F. (215° C.) peak metaltemperatures in a coil oven. Film and end performance properties areshown in Table 22. This material contains 4% GMA and 5% IBMA in theemulsion monomer mix and an acrylic composition with hydroxylfunctionality.

TABLE 21 Beverage End Formulation Composition Example 5 Run 5 Example 3,Run 38 90.80 Dowanol PNP¹ 2.425 Dowanol DPNB¹ 2.425 Isooctyl Alcohol1.54 Michem Lube 160 PFE 0.57 Lanco Glidd 5118² 2.24 Solids (%)27.5-29.5 Viscosity (No. 4 Ford Cup) 20 sec-30 sec ¹Commerciallyavailable from Dow Chemical ²Commercially available lubricant fromLubrizol Corp.

TABLE 22 Film Performance of Beverage End Formulation Water BaseControl¹ Example 5 Run 5 Bake 10 sec to 10 sec to 10 sec to 10 sec toachieve achieve achieve achieve 400° F. 420° F. 400° F. 420° F. (204°C.) (215° C.) (204° C.) (215° C.) MEK Res. 34 40 10 8 Feathering⁴ 0.1780.094 0.074 0.038 Pencil 3H-4H 3H HB HB Hardness COF 0.068 0.076 0.0680.075 Pasteurization² Blush 10 10 9 10 Adhesion 10 10 10 10 WaterRetort³ Blush 9 10 8 9 Adhesion 10 10 10 10 End Continuities InitialAfter Initial After Initial After Initial After Pasteurization² 0.0 0.11.1 17.6 0.5 0.7 0.5 4.3 Water Retort³ 0.05 0.15 1.4 11.2 0.15 0.35 0.7810.5 ¹Commercially available beverage end coating from Valspar coded13Q80AG. ²30 minutes at 85° C. (185° F.). ³90 minutes at 121° C. (250°F.). ⁴Performed after 45 minutes at 85° C. (185° F.) pasteurization.Measured in centimeters.

Results from Table 22 show that a beverage end formulation of thepresent invention can give similar performance to a commercialepoxy-based waterborne beverage end coating even with lower solventresistance as measured by MEK double rubs. There is also an addedbenefit of improved feathering resistance.

Example 6 Latex with Polyester Stabilizer

Example 6 is designed to illustrate the use of a differentacid-functional polymer salt as the stabilizer for an emulsion of thepresent invention.

Stage A

A 2-liter flask was equipped with a stirrer, packed column, Dean Starktrap, reflux condenser, thermocouple, heating mantle and nitrogenblanket. To the flask 700.1 parts dipropylene glycol and 700.1 partsisophthalic acid were added. Under a nitrogen blanket, the contents wereheated to 125° C. At 125° C., 1.05 parts FASCAT 4201 was added. Thetemperature was increased to remove water. At 210° C., water wasbeginning to collect. After an acid number of 5.2 was obtained, 37 partsof xylene was added to aid in the removal of water. An acid number of0.9 was obtained, and a portion of the product was used in Stage B.

Stage B

The material from Stage A (599.8 parts) was placed in a 2-liter flask.The temperature was set at 112° C. and 82 parts trimellitic anhydridewas added. The material was heated to 232° C., and water was removed.After an acid number of 48.4 was obtained, a portion of the material wasused in Stage C.

Stage C

The material from Stage B (198.8 parts) was added to a 2-liter flask,and 40 parts of DOWANOL PNP were added. The material was adjusted to 74°C., and slow addition of deionized water (200 parts) was initiated.After about 30 parts of water were added, 7.6 parts dimethylethanolamine were introduced. When about 150 parts of the deionizedwater were in, heating was halted (the temperature was at 80° C.) and2.4 parts dimethyl ethanolamine were added. After the entire charge ofdeionized water was complete, the viscosity was visually high and 200additional parts deionized water was added. The material was allowed toslowly cool while additional dimethyl ethanolamine was addedincrementally to increase the pH to 6.6. The resulting product was 29.7%solids with an acid number of 53.9.

Stage D

A 500-milliliter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 93.2 parts of the Stage C material and 179 parts deionized water.While the contents of the flask were being heated to 50° C. at 240 RPM,2 drops of HAMP-OL 4.5% Iron and 1.11 parts erythorbic acid were added.In a separate vessel a premix of 28.8 parts styrene, 50.9 BA, 21.0 partsBMA, 5.6 parts IBMA, 4.5 parts GMA and 1.11 parts TRIGONOX A-W70 werepremixed. Once the flask was at 52° C., 10% of the premix was added andheld for 5 minutes. After 5 minutes, the temperature control was set for50° C. and the remaining premix was added over 1 hour. When the additionwas complete, 15.0 parts deionized water was used to rinse the residualpremix into the flask. The batch was then held for 2 hours attemperature, and the batch was cooled. This yielded an emulsion at 34.0%solids, 14.5 acid number, pH of 5.45, and a viscosity 11.5 of seconds(Number 4 Ford Cup).

Stage E

To 50 parts of the emulsion from Stage D, 3.125 parts of a 50/50 blendof ethylene glycol and butyl cellosolve was added. This material wasapplied to chrome treated aluminum panels and baked for 10 seconds toachieve a 420° F. (217° C.) peak metal temperature. Results frombeverage end testing of this example versus a commercial control formulaare shown in Table 23.

TABLE 23 Waterbased Control¹ Example 6 MEK Resistance 22 11 Feathering⁴0.102 0.013 Pasteurization² Blush 10 9.5 Adhesion 10 10 Water Retort³Blush 10 10 Adhesion 10 10 End Continuity Initial 1.35 0.25Pasteurization² 2.38 1.35 ¹Commercially available beverage end coatingfrom Valspar coded 13Q80AG. ²30 minutes at 85° C. (185° F.). ³90 minutesat 121° C. (250° F.). ⁴Performed after 45 minutes at 85° C. (185° F.)pasteurization. Measured in centimeters.

Example 7 Emulsion for Inside Spray

A 3-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 392.2 parts of Example 1: Run 4 acid-functional acrylic, 86.4parts deionized water, 34.6 parts DMEA, and 1120.8 parts deionizedwater. The contents of the flask were heated to 70° C. In a separatevessel a premix of 215.8 parts styrene, 302.7 parts butyl acrylate, and42.0 parts glycidyl methacrylate was prepared. Once the flask was at 70°C., 5.5 parts benzoin and 27.8 parts deionized water was added, followedby 10% of the premix. The flask was heated further to 79° C. and whenthis temperature was reached, 5.5 parts of 35% hydrogen peroxide and27.8 parts deionized water were added and held for 5 minutes. The flaskwas stirred at 210 RPM. After 5 minutes, the temperature control was setat 81° C. and the remaining premix was added over 1 hour. When theaddition was complete, 55.9 parts deionized water were used to rinse theresidual premix into the flask. The batch was held for 10 minutes andthen 0.96 parts benzoin, 55.9 parts deionized water, and 0.95 parts 35%hydrogen peroxide were added. The batch was held for 45 minutes and then0.31 parts benzoin and 0.31 part 35% hydrogen peroxide were added. After2 hours the batch was cooled to 45° C. Once at 45° C., 0.46 part ofHAMP-OL 4.5% Iron 2.98 parts TRIGONOX A-W70, and a premix of 2.1 partserythorbic acid, 0.91 parts DMEA, and 18.0 parts deionized water, wereadded. The batch was held at 45° C. for 1 hour. The material was thencooled to give an emulsion at 31.6% solids, 67.7 acid number, pH of7.04, and a viscosity of 84 seconds (Number 4 Ford cup).

Example 8 Spray Application

The water-based emulsion of Example 7 was successfully formulated into aspray applied coating for the interior of beer/beverage aluminum cans.The product was formulated as described in Table 24.

TABLE 24 Beverage Inside Spray Coating Composition Composition (parts)Example 8 Example 7 material 62.8 Deionized Water 25.3 Butyl Cellosolve5.1 Amyl Alcohol 3.1 Butanol 0.7 Deionized Water 3.0 AdditionalDeionized Water to 18.5% Solids Formulation Solids, % 18.5% Viscosity,No. 4 Ford cup 46 Seconds

This formulation was sprayed at typical laboratory conditions at 120mg/can to 130 mg/can coating weight for the application of interiorbeverage coatings, and cured at 188° C. to 199° C. (measured at the candome) for 30 seconds through a gas oven conveyor at typical heatschedules for this application. The film properties shown in Table 25were achieved.

TABLE 25 Inside Spray Film Properties Water-based Control¹ Example 8Metal Exposures Initial 2 mA 1 mA After drop damage 2 mA 5 mA Waterretort² Blush None None Adhesion Excellent Excellent ¹Commerciallyavailable inside beverage can coating from Valspar coded 10Q45AF. ²90minutes at 250° F. (121° C.)

As can be seen in Table 25, the coatings of the present inventioncompare favorably to the commercial epoxy-acrylate coating

Example 9 Latex with Polyester-Polyether Stabilizer

Example 9 illustrates the use of a different acid-functional polymersalt as the stabilizer for an emulsion of the present invention.

Stage A

A flask was equipped with a stirrer, packed column, Dean Stark trap,reflux condenser, thermocouple, heating mantle and nitrogen blanket. Tothe flask, 809.8 parts sebacic acid and 1283.0 parts CHDM-90 (90%1,4-cyclohexane dimethanol in water) were added. Under a nitrogenblanket, the contents were heated to distill the water from the CHDM-90.While the contents were heated at 165° C., 1.96 parts FASCAT 4100 wasadded. The temperature was increased to 220° C. to remove water. Asample of the batch was tested and found to have an acid number of 0.5.The remainder of the batch was weighed, and to 1711.7 parts of thismaterial were added 1040.2 parts of para-hydroxy benzoic acid. The batchwas heated to 230° C. to remove water. To aid in the removal of water,xylene was added incrementally. After 2 days of water removal, 1.04parts FASCAT 4100 was added to aid in the reaction. The reaction washeld an additional 5 hours and then considered complete. A portion ofthe product was used in Stage B.

Stage B

The material from Stage A (1915.2 parts) was placed in a flask alongwith 823.8 parts ERISYS GE-22 (cyclohexanedimethanol diglycidyl ether,84.8 parts methyl isobutyl ketone (,and 2.63 parts Catalyst 1201(ethyltriphenyl phosphonium iodide,). The temperature was set at 170° C.and the contents heated. After 3 hours at temperature, the epoxy valueof the material was 0.003. The batch was adjusted to have 2684.2 partsof this material in the flask. Added to the flask were 145.0 partsmethyl isobutyl ketone and 294.7 parts succinic anhydride. Thetemperature was maintained at 120-135° C. for 2 hours. After the 2-hourhold, 124.8 parts deionized water and a premix of 214.2 parts DMEA with265.8 parts deionized water were added. Then 6325.8 parts deionizedwater was added. The material was cooled resulting in a product with26.4% solids, an acid number of 71.9, a pH of 7.7, and a viscosity of 15seconds (Number 4 Ford Cup). This material was used in Stage C.

Stage C

A 5-liter flask was equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask wasadded 1183.4 parts of the Stage B material and 779.6 parts deionizedwater. A premix of 7.25 parts erythorbic acid, 6.5 parts DMEA, and 76.7parts deionized water was prepared. This initial premix and 0.18 partsHAMP-OL 4.5% Iron were added to the flask. The contents of the flaskwere heated to 30° C. In a separate vessel a monomer premix of 249.0parts styrene, 113.8 BA, 106.7 parts BMA, 177.8 parts Hydroxy EthylMethacrylate (HEMA), 35.6 parts IBMA, and 28.5 parts GMA was prepared. Athird premix of 7.25 parts TRIGONOX A-W70 and 82.2 parts deionized waterwere made. Once all the premixes were prepared and the flask at 30° C.,the stirrer was set at 240 RPM and all of the monomer premix was added.The monomer premix vessel was rinsed with 81.6 parts deionized water,which was also added to the flask. The contents of the flask werestirred for 10 minutes, after which 10% of the third premix was addedwithin 1 minute. Once the 10% of the third premix was in, thetemperature was increased to 37° C. and the batch was held for 5minutes. After 5 minutes, the remaining amount of the third premix wasadded over 45 minutes. The temperature was allowed to increase with noexternal heat applied. During the addition the maximum temperature was57° C. After the addition was complete the temperature was 51° C.Temperature control was set for 52° C. The third premix was rinsed with108.4 parts deionized water and added to the batch. The batch was heldfor 1.5 hours and then cooled. This yielded an emulsion at 33.1% solids,27.1 acid number, pH of 7.9, and a viscosity of 12 seconds (Number 4Ford Cup).

Stage D

To 1473.75 parts of the emulsion from Stage C, 26.25 parts DMEOA wereadded to increase the pH to 8.6. Using 1330.18 parts of this increasedpH material, 89.51 parts ethylene glycol, 16.65 parts dibasic ester,16.67 parts DOWANOL PM, 5.17 parts xylene, 17.5 parts of a 50% solidssolution of a phenol-formaldehyde phenolic, and 24.57 parts MICHEM 160PFE were added. This formulation was determined to be 30.1% solids, 12seconds Number 4 Ford viscosity and 8.75 pounds per gallon (1.05 kg/l).

The Stage D composition was applied to non-chrome aluminum panels andbaked for 10 seconds to achieve a 420° F. (215° C.) peak metaltemperature. A second set was baked for 10 seconds to achieve a 440° F.(227° C.) peak metal temperature. Results from beverage end testing ofthis example versus a commercial water base and solvent base controlformulas are shown in Tables 26 and 27.

TABLE 26 Comparative Testing of Example 9 Stage D Cured at 420° F. (215°C.) Solvent- Water-based based Example 9 Control¹ Control² Stage D MEK44 34 38 Feathering³ 0.0457 0.0457 0.000 COF 0.061 0.066 0.063Pasteurization⁴ Blush 10 10 8 to 9⁶ Adhesion 10 10 10 Water Retort⁵Blush 10 10 4 to 10⁶ Adhesion 10 10 End Continuity Initial After InitialAfter Initial After Pasteurization 0.08 0.12 0.0 0.30 0.0 0.5 WaterRetort 0.10 0.4 0.02 0.72 0.27 1.2 ¹Commercially available beverage endcoating from Valspar coded 13Q80AG. ²Commercially available beverage endcoating from Valspar coded 92X205S. ³Performed after 45 minutes at 85°C. (185° F.) pasteurization. Measured in centimeters (cm). ⁴30 minutesat 85° C. (185° F.). ⁵90 minutes at 121° C. (250° F.). ⁶Initial Blushseen which improves within 5 minutes.

TABLE 27 Comparative Testing of Example 9 Stage D Cured at 440° F. (227°C.) Solvent- Water-based based Example 9 Control¹ Control² Stage D MEK52 37 40 Feathering³ 0.0559 0.0356 0.000 COF 0.059 0.065 0.063Pasteurization⁴ Blush 10 10 8 to 10⁶ Adhesion 10 10 10 Water Retort⁵Blush 10 10 6 to 10⁶ Adhesion 10 10 End Continuity Initial After InitialAfter Initial After Pasteurization 0.0 0.48 0.07 0.23 0.1 0.8 WaterRetort 0.05 0.4 0.25 1.5 0.35 0.8 ¹Commercially available beverage endcoating from Valspar coded 13Q80AG. ²Commercially available beverage endcoating from Valspar coded 92X205S. ³Performed after 45 minutes at 85°C. (185° F.) pasteurization. Measured in cm. ⁴30 minutes at 85° C. (185°F.). ⁵90 minutes at 121° C. (250° F.). ⁶Initial Blush seen whichimproves within 5 minutes.

Example 10

Example 10 illustrates the use of a different acid-functional polymersalt as the stabilizer for an emulsion of the present invention.

Stage 1

Approximately 1055 parts BPA is placed in a flask along withapproximately 1684 parts of liquid epoxy resin (EPON 828), 85 partsmethyl isobutyl ketone, and 2 to 3 parts Catalyst 1201. The temperatureis set at 160° C. and the contents are then heated for approximately 3hours to achieve an epoxy value of the material of approximately 0.003.The batch is then adjusted to have 2684.2 parts of this material in theflask. Added to the flask is 145.0 parts methyl isobutyl ketone and294.7 parts succinic anhydride. The temperature is maintained at120-135° C. for 2 hours. After the 2-hour hold, 124.8 parts deionizedwater and a premix of 214.2 parts DMEA with 265.8 parts deionized wateris added. Then 6325.8 parts deionized water is added. The material iscooled, and should result in a product with target values of 26% to 27%solids, an acid number of approximately 72, a pH of approximately 7 to9, and a Number 4 Ford viscosity of 15 Seconds. This material is used inStage 2.

Stage 2

A 5-liter flask is equipped with a stirrer, reflux condenser,thermocouple, heating mantle, and nitrogen blanket. Into the flask isadded approximately 1183 parts of the Stage 1 material and 780 partsdeionized water. A premix of 7.25 parts erythorbic acid, 6.5 parts DMEA,and 77 parts deionized water is prepared. This initial premix and 0.18parts HAMP-OL 4.5% Iron are added to the flask. The contents of theflask are heated to 30° C. In a separate vessel a monomer premix of 249parts styrene, 114 BA, 107 parts BMA, 178 parts HEMA, 36 parts IBMA, and28 parts GMA is prepared. A third premix of 7.25 parts TRIGONOX A-W70and 82.2 parts deionized water is made. Once all the premixes areprepared and the flask is at 30° C., the stirrer is set at 240 RPM andall of the monomer premix is added. The monomer premix vessel is rinsedwith 82 parts deionized water, which is also added to the flask. Thecontents of the flask are stirred for 10 minutes, after which 10% of thethird premix is added within 1 minute. Once the 10% is in thetemperature is increased to 37° C. The batch is held for 5 minutes.After 5 minutes, the remaining amount of the third premix is added over45 minutes. The temperature is allowed to increase with no external heatapplied. During the addition, the maximum temperature is 57° C. Afterthe addition is complete, the temperature is set for 52° C. The thirdpremix is rinsed with 109 parts deionized water and added to the batch.The batch is held for 1.5 hours and cooled. This process should yield anemulsion with a target of approximately 33% solids, 27 acid number, pHof 8, and a viscosity of 12 seconds (Number 4 Ford Cup).

Stage 3

To 1474 parts of the emulsion from Stage 2, 26.25 parts DMEOA is addedto increase the pH to 8.6. Using 1330.18 parts of this increased pHmaterial, 89.51 parts ethylene glycol, 16.65 parts dibasic ester, 16.67parts Dowanol PM, 5.17 parts xylene, 17.5 parts of a 50% solids solutionof a phenol-formaldehyde phenolic, and 24.57 parts Michem 160 PFE isadded. This formulation should yield a composition having approximately30% solids.

The Stage 3 composition may be applied to non-chrome aluminum panels andbaked for 10 seconds to achieve a 217° C. peak metal temperature.

Example 11 Stage 1: Preparation of Acrylic Alkali Soluble SupportPolymer

667.6 grams of n-butanol and 33.2 grams of deionized water are chargedto a 5-liter flask equipped with a stirrer, an inert gas inlet, acondenser, and a port for the addition of a monomer feed. This mixturewas then heated to 97° C. to 100° C. under a nitrogen blanket. Next, amixture (hereinafter “monomer premix”) of 853.3 grams of glacialmethacrylic acid, 858.8 grams of styrene, 474.0 grams of ethyl acrylate,63.7 grams of deionized water, and 575.1 grams of n-butanol wasprepared. Another premix (hereinafter “initiator premix 1”) was made ina separate container consisting of 316.3 grams of n-butanol and 113.7grams of Luperox 26 (tert-butyl-peroxy-2-ethylhexenoate). Another premix(hereinafter “initiator premix 2”) consisting of 8.2 grams of n-butanoland 17.6 grams of Luperox 26 was prepared. When the reactor temperaturewas steady at 97° C. to 100° C., initiator premix 2 was charged to thereaction flask and the monomer premix and initiator premix 1 feeds werethen simultaneously started and fed into the reactor over a time periodof 2.5 hours. When the feeds were complete, the flask and feed linescontaining initiator feed one were rinsed with 16.4 grams of n-butanol,then another initiator premix (hereinafter “initiator premix 3”)composed of 29.7 grams of n-butanol and 22.5 grams of Luperox 26 wasstarted and fed into the reactor over the course of 1 hour. Temperaturewas maintained at 97° C. to 100° C. during this feed. When this feed wascomplete, the initiator flask and lines were rinsed with 16.4 grams ofn-butanol and the batch was held at 97° C. to 100° C. for 30 minutes.Following this hold period, a final premix of 4.9 grams of Luperox 26and 0.4 grams of n-butanol was added to the reaction flask. The batchwas then held at 97° C. to 100° C. for 2 more hours. Following this holdperiod, 18.0 grams of deionized water were added to the batch and thebatch was cooled and poured.

Stage 2: Preparation of Emulsion Polymerized Latex Polymer

163.3 grams of the polymer described above in Stage 1 was added to areaction flask equipped with a stirrer, a condenser, an inlet port formaterial additions, and an inert gas inlet. At ambient temperature,under a nitrogen blanket and with agitation, 14.4 grams ofdimethylethanolamine was added to the reaction flask and the resultingmixture was mixed until uniform. Next, 489.4 grams of deionized waterwere added to the flask and the material was heated to reflux to ensurea homogeneity. After the material was homogenous, the mixture was cooledto 40° C. The following monomer mixture was then added to the reactionflask: 89.9 grams of styrene, 126.1 grams of n-butyl acrylate, and 17.5grams of glycidyl methacrylate. The temperature of the flask was allowedto drop. After mixing for approximately 30 minutes, 10.0 grams ofdeionized water and 0.4 grams of tert-butyl hydroperoxide were added tothe reaction flask. Next, a premix of 0.3 grams of erythorbic acid, 0.3grams of dimethylethanolamine, 0.025 grams of a 6.17% aqueous solutionof sodium feredetate, and 25.0 grams of deionized water was fed into thereactor over 15 to 20 minutes. During this feed the acrylic monomersbegan to polymerize exothermically and the temperature was maintainedabove 60° C. for one hour to ensure high conversion of monomer topolymer. After this hold period, 77.4 grams of deionized water wereadded to the batch and the batch was cooled and poured. The molecularweight of the resulting latex polymer was determined by gas permeationchromatography. This data is reported below in Table 28.

TABLE 28 Mw Mn Mp Mw/Mn % Area Peak 1 679,960 361,490 556,920 4.32 76Peak 2 13,720 8,810 15,210 1.56 24

It is believed that peak 1 represents the “batch” polymerized latexcomponent of the polymer and that peak 2 represents the alkali solublesupport polymer.

Example 11 Coating A

In a jar with an agitator, 100 parts of the Example 11, stage 2 emulsionwas stirred with 1.3 parts Michem Lube 160 PF carnauba wax emulsion(available from Michelman, Cincinnati, Ohio, USA). The mixture wasstirred for 10 minutes to make it uniform. The mixture was thenfiltered. The mixture was approximately 32 wt-% solids. The mixture wasapplied at 6-7 milligrams per square inch (msi) (0.94-1.10 mg/cm²) onALX Alcoa aluminum and baked for 10 seconds to achieve a 425° F. (218°C.) peak metal temperature (PMT) in a coil oven.

Example 11 Coating B

In a jar with an agitator, 100 parts of Example 11, stage 2 emulsion wasstirred with 1.3 parts Michem Lube 160 PF carnauba wax emulsion and 2.6parts Durez 33870 phenolic resin (available from Durez Corp., Addison,Tex., USA). The mixture was prepared, cured, and applied to substrate asdescribed above for Coating A.

The coated substrate samples of Coatings A and B were tested alongside acommercial epoxy-acrylate beverage end coating to assess coatingproperties. This data is presented below in Table 29.

TABLE 29 Beverage End Film Properties Epoxy-Acrylate Example 11 Example11 Control Coating A Coating B Film Weight 7.9 msi 6.7 msi 6.4 msi (1.22mg/cm²) (1.04 mg/cm²) (0.99 mg/cm²) MEK Resistance¹ >100 ~2   8Feathering² 0.038    0.004 0 Dowfax³ Blush 7  6T⁶   7T Adhesion 10 10 10  Water Process⁴ Blush  9/10   7/7T   4/10T (in water/above water invapor) Adhesion 10/10 10/10 10/10 (in water/above water in vapor) CoffeeProcess⁵ Stain 2 8 8 Blush 5 8 8 Adhesion 0 10  10  End ContinuitiesInitial N/A 0.5 mA 0.3 mA After Dowfax N/A 7.2 mA 3.0 mA ¹Number ofdouble rubs required to remove the coating using an MEK soaked rag²Performed after 45 minutes at 85° C. pasteurization, measured ininches. ³15 minutes at 100° C. in 0.19% aqueous solution of Dowfax 2A1⁴90 minutes at 121° C. ⁵60 minutes at 121° C. ⁶In Table 29 “T’ standsfor transient, meaning that the blush was temporary and the appearancerecovered after the sample was removed from the test.

Example 12 Polyurethane Dispersion Stage 1: Urethane Prepolymer

To a 2-liter flask equipped with a stirrer, a condenser, a gas inlet,and a thermocouple, the following materials were charged:

159.15 grams of Stepanpol PS-70L polyester (Stepan Corp., Northfield,Ill., USA)

53.04 grams of Terathane 2000 (Invista Corp., Wichita, Kans., USA)

42.67 grams of dimethylol propionic acid

151.36 grams of dicyclohexylmethane 4,4′-diisocyanate

155.49 grams of methyl methacrylate

75.32 grams of dipropyleneglycol dimethyl ether

0.64 grams butylated hydroxytoluene

The mixture was then heated with an air sparge to 88° C. and held attemperature for approximately 3 hours, after which substantially all ofthe hydroxyl groups had been reacted with isocyanate and an isocyanateterminated prepolymer was formed. The prepolymer was then cooled to 60°C. and neutralized with 32.16 grams of triethylamine

Stage 2: Dispersion

In a separate reactor, 1001.57 grams of deionized water and 75.32 gramsof dipropylene glycol dimethylether were chilled to 10° C. The urethaneprepolymer of stage 1 was then dispersed into this mixture of solventand water with good agitation over the course of about 15 minutes. Afterall of the prepolymer had been dispersed, a mixture of 7.88 grams ofethylenediamine and 40.17 grams of deionized water was added to thereactor to chain extend the dispersed polyurethane prepolymer.

Stage 3: Acrylation

After 45 minutes of mixing following the chain extension add, a premixof 214.05 grams of n-butyl acrylate and 45.21 grams of glycidylmethacrylate was added to the reactor followed by 40.17 grams ofdeionized water. The contents of the reactor were mixed for 10 minutes.Next, 1.45 grams of a 70% aqueous solution of tert-butyl hydroperoxidewas added to the reactor. After this addition, a premix of 43.61 gramsof deionized water, 1.07 grams of erythorbic acid, 1.20 grams oftriethylamine, and 0.06 grams of a 6.17% aqueous solution of sodiumferedetate was fed into the reactor over the course of about 15 minutes.An exotherm of approximately 30 to 35° C. occurred during this add asthe methylmethacrylate, n-butyl acrylate, and glycidyl methacrylate werepolymerized. 10.91 grams of water were then added to rinse the additionfunnel and the batch was cooled and poured. The resulting polymerdispersion had a solids content of about 37.9 wt-%, a pH of about 8.3,and a viscosity of 18,000 to 19,000 centipoise.

Example 12 Coating Composition

In a jar with an agitator, 100 parts of the Example 12 dispersion wasstirred with 1.6 parts Michem Lube 160 PF carnauba wax emulsion(available from Michelman, Cincinnati, Ohio, USA) and 4.03 grams of aphenol-formaldehyde crosslinker. The mixture was stirred for 10 minutesto make it uniform. The mixture was then filtered. The mixture wasapproximately 38.2 wt-% solids. The mixture was applied at 6-7 msi(0.94-1.10 mg/cm²) on ALX Alcoa aluminum and baked for 10 seconds toachieve a 465° F. (241° C.) peak metal temperature (PMT) in a coil oven.

The cured films of this material displayed performance characteristicswith respect to beverage end applications similar to that of acommercial epoxy acrylate control.

The instant application is filed on even date with U.S. application Ser.No. ______ (Attorney Docket No. 06 1725 0110) entitled COATINGCOMPOSITIONS FOR CANS AND METHODS OF COATING and U.S. application Ser.No. ______ (Attorney Docket No. 06 1725 0130) entitled COATINGCOMPOSITIONS FOR CANS AND METHODS OF COATING, each of which claimspriority to U.S. application Ser. No. 11/253,161 and is incorporatedherein by reference.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

1. An article, comprising: a body portion or end portion of a food orbeverage can comprising a metal substrate; and a coating compositiondisposed thereon comprising an emulsion polymerized latex polymer that(i) is substantially free of bound bisphenol A and aromatic glycidylether compounds and (ii) comprises the reaction production of anethylenically unsaturated monomer component batch polymerized in thepresence of an aqueous dispersion of a polymer salt.
 2. The article ofclaim 1, wherein the coating composition is disposed on a beverage canend.
 3. The article of claim 1, wherein the polymer salt comprises asalt of an acid- or anhydride-functional polymer.
 4. The article ofclaim 3, wherein the polymer salt comprises a salt of an acid- oranhydride-functional polymer and an amine.
 5. The article of claim 1,wherein the polymer salt is present in the coating composition in anamount comprising at least 5 wt-%, based on the total weight of theethylenically unsaturated monomer component and the polymer salt.
 6. Thearticle of claim 1,wherein the polymer salt comprises an acid- oranhydride-functional acrylic polymer, acid- or anhydride-functionalalkyd resin, acid- or anhydride-functional polyester resin, acid- oranhydride-functional polyurethane, or a combination thereof.
 7. Thearticle of claim 1, wherein the polymer salt comprises a salt of anacrylic polymer.
 8. The article of claim 1, wherein the polymer saltcomprises a salt of a polyurethane polymer.
 9. The article of claim 8,wherein the polymer salt comprises a salt of a polyurethane polymer andan amine.
 10. The article of claim 1, wherein the ethylenicallyunsaturated monomer component is batch polymerized in the presence ofthe aqueous dispersion with a water-soluble free radical initiator at atemperature of 0° C. to 100° C.
 11. The article of claim 10, wherein thefree radical initiator comprises a redox initator.
 12. The article ofclaim 1, wherein the emulsion polymerized latex polymer includes atleast 25 wt-% of the ethylenically unsaturated monomer component, basedon the total weight of the ethylenically unsaturated component and thepolymer salt.
 13. The article of claim 1, wherein at least 40 wt-% ofthe ethylenically unsaturated monomer component comprises an alkylacrylate, a methacrylate, or a combination thereof.
 14. The article ofclaim 1, wherein the emulsion polymerized latex polymer is epoxy-free.15. The article of claim 1, wherein the coating composition issubstantially free of bound bisphenol A and aromatic glycidyl ethercompounds.
 16. The article of claim 1, wherein the coating compositionis present on a food-contact surface of the metal substrate.
 17. Thearticle of claim 1, wherein the coating composition, when present on abeverage can end at a dry film thickness of 7 milligrams per squareinch, passes less than 10 milliamps of current after being exposed for 4seconds to a room-temperature electrolyte solution containing 1% byweight of NaCl dissolved in water.
 18. An article, comprising: a bodyportion or end portion of a food or beverage can comprising a metalsubstrate; and a coating composition disposed thereon comprising anemulsion polymerized latex polymer that (i) is substantially free ofbound bisphenol A and aromatic glycidyl ether compounds and (ii)includes a polymerized ethylenically unsaturated component having anumber average molecular weight of 100,000 or more.
 19. The article ofclaim 18, wherein the polymerized ethylenically unsaturated componenthas a number average molecular weight of 300,000 or more.
 20. A method,comprising: providing a composition comprising an emulsion polymerizedlatex polymer, wherein: (i) the emulsion polymerized latex polymer issubstantially free of bound bisphenol A and aromatic glycidyl ethercompounds, and (ii) the emulsion polymerized latex polymer comprises thereaction product of an ethylenically unsaturated monomer componentpolymerized in the presence of an aqueous dispersion of a polymer,wherein at least about 75 wt-% of the ethylenically unsaturated monomercomponent is present in the aqueous dispersion as unreacted monomerwithin a 1 hour time period during polymerization of the ethylenicallyunsaturated monomer component; and applying the coating composition to ametal substrate prior to or after forming the metal substrate into afood or beverage can or portion thereof.
 21. The method of claim 20,wherein at least about 75 wt-% of the ethylenically unsaturated monomercomponent is present in the aqueous dispersion as unreacted monomer atthe onset of polymerization of the ethylenically unsaturated monomercomponent.